With Justice Scalia’s passing, President Obama has the opportunity to pick another Supreme Court nominee. Any such nominee faces uncertain prospects in the Senate. As we wrote earlier this week, Senate Majority Leader Mitch McConnell faces a strategic dilemma due to competing electoral pressures. In a nutshell, McConnell would prefer to neither vote on, nor obstruct, a Supreme Court nominee before November’s elections, as 24 of the 34 Senate seats up for reelection this year are currently held by the GOP.

It’s a difficult situation for McConnell and his GOP colleagues, because evidence suggests that most Americans want the Senate to seriously consider an Obama nominee. Below, we turn to President Obama’s strategic incentives in this situation.

This isn't the first time

History suggests that Obama can make things very difficult for the Republicans. Not only can he choose to send a nomination to the Senate — which we have argued that McConnell would prefer to avoid — but Obama also gets to choose whom he will nominate: He could nominate a well-known liberal, a well-known conservative, or someone seen as a centrist. The combination of the current ideological composition of the Court and the fractured condition of the GOP’s electoral base grants Obama a particularly powerful agenda-setting position, especially relative to the GOP’s electoral situation heading into November.

A historical perspective

The Republican Party is in many ways similar right now to the Democratic Party of the mid-20th century. It comprises a precarious coalition of groups with strong preferences that on any given issue could oppose each other. For the Democrats, the tension was between liberal progressives in the North and the Dixiecrats in the South. If we consider Supreme Court nominations and confirmations from that era, we see a distinct pattern of Democrats splitting.

That began in particular with the nomination of Justice John Marshall Harlan II. Harlan’s nomination by President Eisenhower in the wake of the Court’s decision in Brown v. Board of Education split the Democratic Party, which held 46 of the 96 seats in the Senate (there were also two independents).

That general pattern continued throughout the following 20 years, most notably coming to a head with President Johnson’s nomination of Abe Fortas to be elevated from associate justice to chief justice in 1968, prompting a filibuster that was sustained in part by Southern Dixiecrats siding with Republicans.

For the modern Republican Party, the tension is between pro-business, small-government interests and social conservatives. A strategic choice of a nominee by Obama might split these groups, who could never agree on a pro-choice, libertarian judge. Consider, for example, a nominee who opposes regulations on both guns and abortion. Or a judge who opposes campaign finance reform but supports marriage equality. Such a split would further divide the party in the months before the election, especially if it implicates an extended battle over social issues, on which Democrats have a distinct advantage among the electorate.

Putting some chips on the table: thinking about Obama's incentives

So whom should Obama nominate? There have been many takes on this, so we’ll focus on the strategic side, rather than on the idiosyncrasies of the possible candidates. To keep it simple, consider three types of nominees: a liberal, a centrist, and a (moderate) conservative. Examples of liberal picks would include Elizabeth Warren, Tom Perez, and Debo Adegbile; centrists would include Sri Srinivasan, Patricia Ann Millett, and Merrick Garland; moderate conservatives would include Jeffrey Sutton, Paul Clement, and Sen. Mike Lee.

The liberal and conservative options are the easiest to prognosticate about, so we’ll dispense with them first. We begin with what we see as the option that is least likely and least attractive from Obama’s standpoint — nominating a liberal — and then consider the conservative option (which has attracted a lot of attention) before moving to the truly interesting case: the uncertain centrist.

Option 1: Playing to the base

A liberal pick would presumably be blocked by the GOP but might “energize” Democratic voters heading into the 2016 elections, a potential mobilization benefit. The principal risk here for Obama is that he misses an opportunity to actually influence the Court. A secondary, but not trivial, risk is that he passes up the opportunity to paint the GOP senators as unreasonable, as we discussed in our earlier post.

Taking the liberal option requires believing that the “mass mobilization” effect of the nominee outweighs both the policy/legacy incentives from seeing a nominee confirmed and the (Senate and potentially presidential) electoral gains from painting the incumbent GOP senators as obstructionist. First, it is uncertain how much a nominee will actually mobilize voters, and even if it does, political science research (see Flavin and Griffin [2009]) indicates that mobilizing actions by presidents tend to mobilize both allies and opponents. Thus, this route is unlikely to end up being President Obama’s best choice.

Another concern on this front, which we note in passing, is that it is unclear why a qualified liberal candidate would accept the nomination — even if President Obama wanted to choose one, he might have a hard time finding a willing taker. With that said, we move on to the case of a moderate conservative nominee.

Option 2: Compromise, but with honor

A moderate conservative would have the best chance of getting confirmed by the GOP given the current makeup of the Senate, but would also represent a bit of a acquiescence by Obama given the possibility of Democratic gains in the Senate this November and the currently very muddy waters of the fight for the Republican presidential nomination.

That said, on Wednesday it was reported that Obama had been considering Brian Sandoval for the vacancy. Sandoval has since taken himself out of consideration, but the important points to note about him (or another candidate like him) is that he is a political centrist, which means that if the Senate were to confirm him, Obama could still argue he has moved the Court to the left. Sandoval supports abortion rights and is not actively opposed to same-sex marriage, but is an opponent of gun control measures. That combination — pro-choice and anti-gun control — might be exactly the kind of poison pill that could rip the GOP apart. While he’s not exactly popular with the GOP establishment, he has great credentials, having previously served as a federal judge. (He was nominated by George W. Bush in 2004 and confirmed in a unanimous vote.)

A nominee like Sandoval would have put the GOP in the Senate in a very tricky position. However, it might have been the worst option for President Obama. If Mitch McConnell could have withstood any pressure from his caucus to hold hearings on Sandoval, then the inference the public might have drawn is that McConnell and the GOP really are standing on principle rather than stonewalling on ideological grounds. However, the more moderate members of the Senate GOP would likely have faced a lot of political pressure from their electorates to at least consider Sandoval.

Unlike the liberal option discussed above, this route does have some draw, if only because it represents the highest probability of installing a new justice whose voting will presumably be at least slightly more liberal than was Justice Scalia’s. It also has the uncertain possibility of imposing electoral costs on the 24 GOP Senate incumbents who are up for reelection in November.

Also unlike the liberal option above, it forestalls the opportunity for a new president to move the Court in a more appealing ideological direction. This is especially pertinent if the Democratic Party maintains control of the presidency, but it might also be the case for any new Republican president — especially Donald Trump. We’ll leave the details by the side for now, but any newly elected president probably arrives with a bit of political capital (particularly with respect to appointing a Supreme Court Justice to a court that, by that point, would have been down one member for around a year or more).

It’s also highly unlikely that the GOP is going to have a filibuster-proof 60-seat majority in 2017, so the president, regardless of party, will have to appease both moderate Republicans and moderate Democrats.

Finally, let’s turn to the wild card: the “centrist.”

Option 3: Centrist … or wild card?

Given the weaknesses of the liberal and conservative strategies, the Goldilocks principle suggests that the centrist strategy might be “just right.” After all, the properly chosen centrist would seem to balance the mobilization, ideology, and policy concerns that are imbalanced under either the liberal or conservative strategy. This is undoubtedly true … if one can actually find a true centrist nominee.

Our objection is not that there are no true centrist nominees. Rather, it is important to note that centrists are hard to find, almost by definition1. In terms of liberal/conservative ideology, a centrist is defined by what he or she is not. Just like legislators, justices are (essentially) asked to either support or oppose a particular decision. Because of this, a “centrist” with respect to scientific measures like the Martin-Quinn scores is not necessarily an individual who chooses “the middle” (see this recent discussion by David Broockman).

Being centrist definitely could indicate that an individual is a principled centrist and, in a principled fashion, votes liberally on some issues and conservative on others. It can also indicate someone who votes in an uncertain fashion on many, or all, issues. For example, somebody who uses a Magic 8-Ball to choose his or her votes will, in expectation, be coded as a “centrist,” when he or she is probably better labeled as a “wild card.”

This uncertainty mitigates the appeal of the balance of the three motivations — mobilization, ideology, and policy — that a centrist nominee appears to present to President Obama. First, Obama is probably uncertain about the true colors/voting tendencies of the centrist candidates. But even if he is not, it is important to realize that, in terms of policy, Obama can fully benefit from appointing a centrist only if a large group of senators also have no uncertainty. After all, he will get the policy benefits only if the Senate confirms the nominee. (Recall the defeat of Harriet Miers, which was largely attributed to GOP senators’ uncertainty about whether she was reliably conservative.)

Similarly, a centrist who has judicial experience will have a centrist and, hence, “conflicted/complicated,” record of positions on various issues. So even if a senator — regardless of partisanship — is sure about a centrist nominee, how does that senator explain the nominee as a centrist to his or her constituents, especially in the glare of what will be a high-profile vetting and confirmation process?

So what to do — and who to choose?

In the end, and as always when analyzing politics “in real time,” there are many details about the motivations and beliefs of individuals such as President Obama, Majority Leader McConnell, and his colleagues in the Senate to which we are not privy. Many of these details involve “higher order” beliefs such as how Obama believes Sens. McConnell and Chuck Grassley (R-IA), chair of the Senate Judiciary Committee, will react to various potential nominees.

That said, our cautious advice would be that President Obama should nominate a moderate conservative to the Court. We say this while acknowledging that there is no perfect — and definitely no certainly perfect — choice. That’s simply the nature of the situation.

Nonetheless, while there is some “policy” risk that the Senate might confirm the appointee when a more liberal justice could have been confirmed in 2017, the stonewalling and obstruction that is likely to follow from McConnell and Grassley digging their heels into the sand may obviate that possibility by refusing to confirm the nominee. At the very least, it will make the GOP look fractured and ideologically extreme as they proceed in a haphazard way to ultimately confirming the choice.

In the immediate wake of Justice Scalia’s death, Senate Majority Leader Mitch McConnell very quickly announced that President Obama should not name Scalia’s successor. A great deal of attention has been paid (including by the Onion) to the political posturing that has taken place in the hours and days since.

Understandably, much of it focuses on what kind of nominee might actually be nominated and whether such a nominee would actually be confirmed. We’re going to take a different tack and consider why McConnell so quickly tried to preempt a nominee in the first place.

There's no harm in looking, right?

Formally, it is very easy for McConnell and his Republican colleagues to ensure that no Obama nominee would be confirmed (though the Democrats could make life difficult). Given this, then standard “gatekeeping” logic (see here) implies that the GOP can only gain from at least seeing whom Obama would nominate: If Obama nominates an unacceptable nominee, the GOP senators can simply say no to whomever Obama nominates.

Furthermore, withstanding the pressure to vote on an Obama nominee could help GOP incumbents signal their commitment to the conservative principles, such as gun rights, that Scalia stood for on the Court. This logic is laid out by one of us in “Signaling Through Obstruction” (ungated version).

The fear of being seen as extreme

However, from a strategic standpoint, McConnell might fear that 14 or more of his colleagues would not be willing to obstruct a moderate and well-qualified nominee. In fact, some senators might actually be willing to vote for a relatively liberal nominee because they fear being perceived as too conservative by moderate voters. This logic lies at the heart of the reaction described by Tim Groseclose and Nolan McCarty.

The possibility of incumbents fearing the blame game is unusually important for McConnell this year because the GOP has 24 Senate incumbents up for reelection this year, and of the 12 competitive Senate races this year, 10 are for seats currently held by Republicans.

Naturally, most of those competitive seats are in states where the electorate is relatively more moderate — places like Illinois (Mark Kirk), Missouri (Roy Blunt), North Carolina (Richard Burr), New Hampshire (Kelly Ayotte), and Ohio (Rob Portman). Such incumbents might worry that obstruction would be too costly in terms of alienating independent voters in the general election. Indeed, see Kirk’s op-ed from Monday, in which he wrote:

I recognize the right of the president, be it Republican or Democrat, to place before the Senate a nominee for the Supreme Court and I fully expect and look forward to President Barack Obama advancing a nominee for the Senate to consider.

The devil's in the details

Putting the “Signaling Through Obstruction” and “Blame Game” logics together creates a rich set of scenarios for McConnell, who is undoubtedly uncertain not only about how the electoral environments facing his 24 colleagues will unfold, but also about how these colleagues will behave as the election progresses. Accordingly, he may have a strong incentive to avoid forcing his colleagues to go “on the record” with either a vote on a Supreme Court nominee, or with being seen as complicit in obstructing one, particularly one who will likely be widely perceived as extremely qualified and politically moderate.

After all, if there is no nominee to vote for or obstruct, voters cannot infer much, if anything, about their incumbents’ stances from their actions. As has been well documented by political science research (see here and here for examples), senators are sensitive to opinion among their political base when voting on Supreme Court nominees. At the same time, well-qualified, moderate nominees tend to be broadly politically popular.

In other words, the problem for McConnell is that if President Obama selects a well-qualified, politically moderate nominee, Republicans will have to decide whether to go on the record voting against the nominee, revealing themselves to be ideological extremists, or to support a political moderate, nominated by President Obama, potentially upsetting their political bases. In the context of a competitive election, the choice is then between the base and independents, both of which are necessary to win reelection in closely divided states.

In line with all of this, and as one of us has pointed out in another post, there may be a strong interest among Democrats in keeping the nomination debate going as part of the election, whereas Republicans might have a distinct interest in ending the discussion (or at least hiding it from public discussion until after the election).

Weighing 34 Senate races against one presidential election

Many have speculated that McConnell’s reluctance is due to his hope that a future Republican president might nominate Justice Scalia’s replacement. However, our logic suggests a different rationale. Given President Obama’s relatively constrained political capital and the GOP’s control of the Senate, this seems like a good opportunity for the Republicans to press Obama for a moderate nominee. However, that might be exactly what McConnell fears!

McConnell’s desire to preempt any Obama nominee is motivated by the fear that, when confronted by a nominee, his GOP colleagues will confront a Catch-22 in which, regardless of what they say or do, the GOP’s prospects for maintaining control of the Senate in 2017 will be worsened. Scalia’s passing rocked the political scene, and left Mitch McConnell in a very hard place indeed.

Justice Antonin Scalia’s passing has prompted a lot of discussion about his role as a leader of the conservative bloc on the Supreme Court during the past 25 years. Indeed, Scalia was well known as a judicial conservative firebrand. However, he was also known for being a bit of a maverick on some issues.

For example, he was a fairly strong supporter of free speech rights. He recounted at least once that after his vote to support the right to burn the American flag, he received some criticism for his position. In addition, Scalia was known to often side with the more typically liberal members of the Court in cases involving search and seizure and other criminal defendant rights.

In research I have done with Benjamin Lauderdale of the London School of Economics and Political Science, we studied how the justices’ voting varies across substantive areas of the law (see also here and here). We find there that those general impressions are confirmed by the data — Scalia was most likely to be one of the more moderate justices in cases involving criminal procedure and search and seizure, in particular.

That pattern is particularly important for progressives as they evaluate the person President Barack Obama might nominate and as they move through the current campaign season. Some well-known liberal justices have historically been more moderate on issues of criminal procedure.

To return to the example of search and seizure, Scalia often found himself voting with the more liberal members of the Court and against Justice Stephen Breyer — a typically more liberal justice — who in those cases sided with the more traditionally conservative justices. Examples of such cases include Kyllo v. United States (2005), Arizona v. Gant (2009), Florida v. Jardines (2013), Missouri v. McNeely (2013), Maryland v. King (2013), and Navarette v. California (2014).

Since 2000, the Supreme Court has decided 12 search and seizure cases by a vote margin of 5-4. So in as many as half of the divided search and seizure cases this century, a justice in the mold of Breyer, rather than Scalia, could have produced a more conservative outcome. Progressives should be particularly thoughtful about this issue as they contemplate the consequences of replacing Scalia on the Court.

These concerns could be particularly sharp if Obama is forced, by political pressure, to nominate a more moderate justice, who could make it through the confirmation process when Obama is politically weak and facing a recalcitrant Senate. Because he confronts a recalcitrant Senate, one strategy forward for Obama might be to choose a nominee who splits the Republican senators — trying to “peel off” enough votes from the GOP to side with his Democratic allies and get the nominee through the confirmation process. This kind of moderation might be particularly painful for progressives if it undermines the few areas where they have had some success in the Court during the past decade.

The issue here goes further than just how search and seizure cases will be decided in the future. Dana Milbank points out that the Supreme Court is more typically associated with social issues than with economic ones. The consequence is that turning the presidential election into a debate about the Supreme Court could be good for Democrats, who have an electoral advantage on those issues.

(This is ironic, given that the most frequently litigated laws before the Supreme Court include the Internal Revenue Code, the National Labor Relations Act, the Bankruptcy Code, and the Sherman Antitrust Act. Of course, the most litigated legal provisions also include the First, 14th, and Fourth Amendments.)

If this is correct — and some have argued it is not — then progressives might also be leery about hurrying through the nomination process. They may instead opt to drag out the debate through the rest of the campaign season to keep people’s minds focused on the consequences those political issues might face with a conservative president.

So, to conclude, it seems progressives might benefit from keeping the current vacancy open. If a Democrat is elected in the fall, which has a better than ever chance of happening, then the nomination will come from someone with a current political mandate (and possibly even a Democratic majority in the Senate).

The consequence will be a less moderate justice, and less risk of moving the Court to the right on the few issues where Justice Scalia was relatively more moderate. And in the meantime, the Democrats could benefit from forcing social issues onto the agenda, where they have traditionally held a political advantage.

Tom Clark is the Asa Griggs Candler professor of political science at Emory University.