The Democratic Party once maintained a reputation for persistent fractiousness and rebellious challenges to veteran party leaders, while the Republicans were traditionally held to be politically homogeneous and respectful of authority. Humorist Will Rogers quipped in the 1930s that “I don’t belong to an organized political party — I’m a Democrat,” while then-House Majority Leader Tip O’Neill observed a generation later that “we Democrats are all under one tent. In any other country, we’d be five splinter parties.”

More recently, recurrent internal battles over legislation, strategy, and leadership posts have become a familiar characteristic of the congressional Republican Party, while the Democratic opposition appears placid and orderly by comparison.

In our new book, Asymmetric Politics: Ideological Republicans and Group Interest Democrats, we explain why the congressional parties have come to behave so differently. Because the Republican Party is defined by its adherence to the symbolic cause of conservatism, Republican officeholders pledge fidelity to a set of abstract values.

In eras when conservatives largely agree about how their ideological commitments are best advanced in practice, the party appears relatively unified and harmonious. When significant internal disputes arise — a regular occurrence during the Obama presidency — they tend to take the form of accusations from one faction of Republicans that their fellow partisans have betrayed conservative principles.

The Democratic Party, in contrast, has consistently maintained the character of a coalition of social groups more preoccupied with pragmatically seeking concrete benefits from government than with advancing a larger ideological cause. Disagreements among Democrats tend to divide the interests of one group or set of groups from another.

In previous decades, when the coalition included white Southerners and conservative Catholics as well as racial minorities and left-leaning intellectuals, forging compromise was a particularly difficult task for the Democratic leadership. Today, the constituent elements of the coalition are more mutually compatible in their policy preferences, although party leaders must still work to satisfy the policy priorities of each group without the ability to appeal to a common ideological commitment.

Why Republicans leaders fail to govern despite electoral success

The speakership of John Boehner was wildly successful in electoral terms — House Republicans gained 63 seats under Boehner’s leadership in the 2010 midterm elections and held more seats in the chamber at the time of Boehner’s departure last October than at any point since the 1920s — but ultimately fell prey to a bloc of disaffected purists within his party.

Most members of this hard-line faction have become associated with an organization known as the House Freedom Caucus, a name that reflects their claims of unswerving devotion to conservative principles. Boehner found it impossible to satisfy these critics while simultaneously pursuing the compromises required to move necessary legislation, such as spending bills and hikes in the federal debt ceiling, through Congress.

The pro- and anti-Boehner factions within the House Republican Party both identified as ideologically conservative and took similar positions on most public policy matters. But the divisions between them proved impossible for the former speaker to bridge.

An ideologically oriented party is inherently vulnerable to the accusation that its governing record has failed to honor its philosophical commitments, especially in a separation-of-powers system, which often requires occasional cooperation with the partisan opposition. Dealmaking is not a promising approach to the resolution of political disputes when one side is primarily occupied with preserving its record of ideological purity, especially when this uncompromising approach is encouraged by many activists and powerful media personalities within the party.

Some critics of Congress have suggested that the institution restore the practice of earmarks in order to grease the wheels of the legislative apparatus, but such a measure is unlikely to change the behavior of members who have dedicated themselves to the conspicuous pursuit of ideological principles over transactional politics.

Why the left fails to challenge congressional Democrats

In an era when congressional polarization is widely assumed to be the product of comparable trends on both sides of the partisan aisle, it is worth considering why no left-wing equivalent to the House Freedom Caucus — or counterparts in the Senate, like Ted Cruz of Texas — has emerged to demand regular displays of ideological purity and to launch internal challenges to the Democratic leadership.

Our analysis suggests that this asymmetry reflects the Democrats’ foundational nature as a coalitional rather than an ideological party. The most influential constituencies within the Democratic electoral and activist base — such as labor unions, racial minorities, environmentalists, and the economically disadvantaged — maintain an extensive wish list of specific policy priorities, encouraging Democratic officeholders to work pragmatically to enact an ambitious legislative agenda rather than engaging in symbolic acts of philosophical devotion.

The coalitional nature of the Democrats does not always work to the party’s advantage. As Boehner’s Democratic predecessor Nancy Pelosi discovered, the concessions and compromises required to successfully steer major legislation through Congress can result in significant flaws —such as the well-documented imperfections of the Affordable Care Act (ACA).

But the relative lack of strict ideological litmus tests enforced by party members and activists both inside and outside Congress allows Democratic leaders greater freedom of movement to satisfy, even if incompletely, the demands of their party’s most attentive supporters, preventing Democrats from succumbing to the same series of internal revolts and governing crises that have repeatedly befallen the GOP.

Some liberals were disappointed that the ACA did not contain a public option or establish a single-payer health care system, but even the most left-wing Democrats in Congress chose to support a bill that they viewed as a partial solution rather than declare it unacceptably inconsistent with their principles.

Expect little change in the behavior of the congressional parties

Conservative purists such as the members of the House Freedom Caucus are often derided by veteran Washingtonians of both parties as either cynical grandstanders or extremist “wacko birds,” in the memorable phrase of critic John McCain. Yet their criticisms of Republican leaders for failing to uphold their own conservative commitments contain, at heart, an unavoidable grain of truth.

Even “establishment” Republicans like John Boehner have been fond of engaging in campaign rhetoric that advocates a dramatic, and even revolutionary, reduction of the size and scope of the federal government, as well as a return to traditional cultural norms and mores.

The repeated failure of Republicans to deliver on these ambitious promises when in power — in large part because popular enthusiasm for a smaller government largely dissipates once the debate shifts to the specific programs and benefits that would need to be cut in order to realize it — only further justifies the frustrations of conservative activists.

Though Boehner has surrendered the speaker’s gavel, his departure does not resolve the tensions roiling a congressional party that often finds itself caught between its ideological commitments and its electoral fortunes. Unless Paul Ryan can devise a solution to this dilemma, he may become its next victim.

Matt Grossmann is the director of the Institute for Public Policy and Social Research at Michigan State University. David A. Hopkins is an assistant professor of political science at Boston College. They are the authors of Asymmetric Politics: Ideological Republicans and Group Interest Democrats.

During the congressional debate over the Affordable Care Act (ACA), Republicans successfully undermined overall popular support for the law by characterizing it as a “government takeover” of the American health care system — even though most of its specific provisions remained quite popular with the public.

As many frustrated Democrats pointed out, the ACA was far from the exercise in single-payer socialized medicine implied by Republican critics. In fact, the law’s structure is striking for the many ways in which it attempts to avoid conservative accusations of “big government” liberalism.

Republicans favor federalism over nationalization. The ACA creates state-based insurance exchanges and uses state Medicaid partnerships to deliver services.

Republicans favor private sector implementation over increasing government bureaucracy. The ACA delivers benefits mainly through private insurance companies.

Republicans favor free market incentives. The ACA uses internet-based shopping marketplaces, which allows consumers to compare prices and requires insurers to compete for their business.

But the purpose of the ACA reflects a longtime objective of the Democratic Party: using government policy to provide better health care coverage to a greater number of people.

Like most American policy, the ACA uses Republican forms of governance to address Democratic constituency concerns

In our new book, Asymmetric Politics: Ideological Republicans and Group Interest Democrats, we argue that this pattern is typical of American public policy: Political leaders typically pursue the goals of Democratic constituencies using tools and approaches that respond to conservative critiques of big government.

Because the Democratic Party is a coalition of social groups seeking concrete political objectives, Democratic politicians are willing to compromise over the methods of policy implementation in the service of delivering practical benefits to group members. As an ideological movement, the Republican Party characterizes each set of new initiatives as expanding the role of government in violation of constitutional values.

To achieve their substantive objectives, Democrats compromise over the form of policy implementation in an (often futile) effort to appease Republicans and prevent internal dissension

The result is a policy infrastructure built mainly by pragmatic Democrats (and a near-extinct faction of moderate Republicans) that is liberal in its ends but conservative in its means. To achieve their substantive objectives, Democrats compromise over the form of policy implementation in an (often futile) effort to appease Republicans and prevent internal dissension.

During the consideration of the ACA, Democrats offered modifications to the law not only to appeal to a few Republicans but also to address specific concerns voiced by business groups, Congressional Black Caucus members, pro-life Democrats, and unions.

Democratic leaders and activists have plenty of policy goals, but they fail to agree on an ideological vision for a larger government role in society; many Democrats have even internalized conservative criticisms of federal agencies and programs.

As a result, public policy responds to conservative critiques. One example is federalism. The figure below compares the size of the federal workforce to state and local public sector employment since 1946. It shows that the American political system has decentralized the work of government, increasingly shifting it below the national level.

Yet these state and local employees are often supported by federal largesse or mandated by federal requirements — and they are not alone. Public policy increasingly relies on private sector government contractors and recipients of competitive grants (usually nonprofits) to deliver services. Although it is difficult to measure the size of this “shadow government” with precision, it now eclipses that of the direct federal workforce.

American public policy also relies on the delivery of benefits through subsidized private sector expenditures, such as the individual insurance markets created by the ACA. Data collected by Jacob Hacker and summarized in the figure below confirms that American social welfare spending nearly matches that of large European nations — but a large fraction of our welfare spending passes indirectly through private companies, usually employers.

These decentralized and private sector–dependent forms of American policy are often permanent, once they are included in the initial designs of policy.

The ACA is also emblematic of the American state’s tendency to rely on tax credits and exclusions, with benefits delivered through a highly complex tax code rather than through direct transfer payments or new government bureaucracies that would attract opposition from conservatives. The graph below compares discretionary federal spending with tax expenditures, or foregone revenue attributable to legislated tax benefits. It shows that these benefits now collectively match those provided by non-entitlement spending.

American public policy is the product of compromises between asymmetric parties

Given the polarized character of contemporary American politics, observers often assume that the two parties rigidly adhere to diametrically opposed policy preferences and principles (and are thus unable to find any common ground).

But the content of American public policy shows that the parties have reached a grand compromise of sorts over the past 50 years: Republicans have prevented large new government bureaucracies but not slowed the growth of new policy goals. Democrats have collectively expanded the scope of government authority but have been forced to implement their initiatives in cooperation with the private sector, by relying upon market competition and tax incentives, and by decentralizing services to states, localities, contractors, and grantees.

Critics habitually complain that out-of-touch politicians ignore the will of the citizens they serve. But the American public, which collectively distrusts government in general even as it favors maintaining and even expanding government’s specific responsibilities, has mostly gotten its (self-contradictory) way.

There is a cost, however, to this incoherent responsiveness, visible in the ever-more-complicated and imperfectly realized manner in which public policy is created and implemented in the United States. As long as voters continue to prefer a smaller government that tries to solve a growing number of specific social problems, the two major parties will try their best to reconcile these inconsistent demands.

Matt Grossmann is the director of the Institute for Public Policy and Social Research at Michigan State University. David A. Hopkins is an assistant professor of political science at Boston College. They are the authors of Asymmetric Politics: Ideological Republicans and Group Interest Democrats.

Bernie Sanders spent the 2016 primary campaign vowing to lead a political revolution that would fundamentally reform American politics. Like Sanders, many liberals believe that an unfair and corrupt political system controlled by privileged interests represents the chief obstacle to the realization of an otherwise popular left-wing agenda. Enacting reforms to the electoral and legislative process, they argue, would effectively remove this barrier, quickly producing a decisive leftward shift in the trajectory of national policy.

Yet history does not support this view. Liberals in the 1970s also believed that institutions were holding back the advancement of their favored policies. They sought and achieved reforms in campaign finance, party nominations, government transparency, and congressional organization that were designed to depose moderate and conservative Democratic leaders while bolstering the influence of liberal activists at the expense of “establishment” interest groups. Rather than usher in a period of ambitious liberal achievements, these reforms in fact coincided with the close of an era of left-of-center policy change.

We explore the reasons for this failure in our new book, Asymmetric Politics: Ideological Republicans and Group Interest Democrats. Our analysis finds that the Democratic Party is a coalition of social groups, each with pragmatic policy concerns. This party structure was well adapted to a policymaking process that required brokering compromises among a large set of discrete interests to pass legislation, especially within a system of multiple congressional committees aligned with associated interest organizations and constituencies.

Scholars often treat the institutional reforms of the mid-1970s as enabling the transformation of the institutionally decentralized, ideologically incoherent, and interest-governed Democrats into a more unified, nationalized, liberal-dominated party. But our best measures of congressional ideology (displayed in the graph below) show that the Democratic Party has collectively moved only modestly to the left since that era, mostly due to the attrition of its conservative Southern wing.

Congressional Republicans, meanwhile, shifted abruptly to the right and never turned back — even as they captured a growing share of seats in both the House and Senate. The post-reform political system has allowed the flourishing of the more ideologically oriented party: the Republicans.

Like Sanders supporters in 2016, the reformers of the 1970s believed the public would reward policymakers who pursued myriad liberal policy objectives favored by voters — but it did not turn out that way. While the American public takes left-of-center positions on many specific policy issues, it also holds generally conservative views on the size and role of government, giving the Republican Party fertile ground to stoke a popular backlash against “big-government” liberalism.

The institutional reforms also did not produce the policy successes that liberals expected. New policies and programs were adopted at a declining rate after the mid-1970s, reflecting a rightward ideological shift in national politics.

The solid line in the graph below represents the number of significant domestic policy changes identified by policy historians in each two-year period. The dashed line represents the number of net liberal policy changes (liberal minus conservative changes). As the figure reveals, the pre-reform era of the 1960s and early ’70s marked the high tide of both net policy liberalism and policymaking productivity.

We do not claim that institutional reforms caused the decline in liberal policymaking, but there is certainly no evidence that reform led to the expected burst of new successes. A congressional GOP that was both growing in size and steadily moving to the ideological right was regularly able to block significant legislation. The increasingly diverse Democratic Party was never able to mount a return to the level of policy achievements that it reached in the 1960s.

Broader party and campaign reforms also failed to counter the influence of money in politics, but may have furthered the breakdown of previous cozy relationships between committees and Democratic-aligned interest groups and constituencies.

Note that the historical record gives conservatives good reason to be skeptical of legislative productivity: More new laws usually mean a shift to the ideological left.

As a result, Republican officeholders often focus more on blocking Democratic initiatives than on developing their own alternatives, concentrating instead on broader fights over taxation and the federal budget. We find that Congress is more productive under Democratic rule — not only in policymaking but also in committee hearings and in the number of substantive topics considered. In addition, Democratic presidents send far more new policy proposals to Congress and make more administrative changes within the executive branch.

The best measure of legislative effectiveness controls for these large differences in partisan productivity across time to focus on comparing legislators serving contemporaneously, but it still reveals important party differences. The graph below reports the relative success of each party’s members in passing significant, as well as less important, legislation. Democratic committee chairs tend to be particularly effective at passing major bills, perhaps suggesting the benefits of the prior committee-based system for the Democratic Party. Republican backbenchers are surprisingly good at passing less important bills.

Each party’s unique approach to governing has important implications for reform of political institutions. The Democratic Party, as a coalition of social groups with multiple policy demands, seeks to regularly pass more legislation. The Republican Party, as the agent of an ideological movement opposed to government intervention and social change, is less active in policymaking overall.

As ambitious liberals consider proposals for future reform, they should assess whether each potential change is likely to benefit the Democratic coalition or the more ideological Republicans. History suggests reforms, once instituted, may not always have the effect that their advocates intend.

Matt Grossmann is the director of the Institute for Public Policy and Social Research at Michigan State University. David A. Hopkins is an assistant professor of political science at Boston College. They are the authors of Asymmetric Politics: Ideological Republicans and Group Interest Democrats.