Why is Donald Trump the GOP nominee? Two words: Hillary Clinton.

The presidential race is an absolute mess. Both parties are fielding unpopular candidates, the electoral map is topsy-turvy, and major party figures in the GOP are publicly stating that they will vote for the Democratic nominee.
What happened? Did “the parties” fail? More specifically, why is Donald Trump, a B-list celebrity with a checkered past and no history of public service, now the nominee of a major party?

On its face, this seems at odds with social science. After all, one justification for political primaries is that they sort the wheat from the chaff. The contenders survive while the pretenders fall by the side, and so forth. But here we are.
In the end, this is a complicated question, to be sure. That said, there is a nugget of theoretical political science that arguably offers some understanding of how this happened. I’ll admit, this is with the benefit of hindsight — the theory in question was aimed previously at races for “lower” and more numerous offices, such as legislative races. But after thinking about it for a few days, there is some plausibility that warrants attention.

The logic, as expounded by Jeffrey Banks and Rod Kiewiet in this 1989 article, is simple and elegant. In their formulation, low-quality challengers run against strong incumbents since they know they can’t wait to run against a weak incumbent, because high-quality challengers are waiting for such an opportunity.
Banks and Kiewiet are explaining why low-quality challengers run at all, which is not really a question for presidential races. After all, this year, the Federal Election Commission (FEC) has so far recorded 4,608 candidates for president. People run for a variety of reasons not related to winning. The heart of Banks and Kiewiet’s theory is really why the good candidates don’t run. One can expand this easily to why “good candidates don’t run hard.” Their answer is that good candidates can wait and run when they want — which, in a nutshell, is when they can face a weaker opponent.

To quote Sun Tzu, “...the victorious strategist only seeks battle after the victory has been won, whereas he who is destined to defeat first fights and afterwards looks for victory.”

Applying this to the 2016 presidential campaign, it was clear at the beginning that Hillary Clinton would be a formidable opponent. Experience, name recognition, endorsements, and funds on hand were hers from the outset. Given that hill to climb, who would run — and run hard — in the GOP primary battle to secure the opportunity to face off against her?

I am not saying, of course, that Clinton was seen as — or is — unbeatable. Indeed, she has well-known vulnerabilities, as all of our home email servers do. Instead, I am pointing out that a race against Clinton was going to be tough — and arguably tougher than usual — for anyone.

Especially for younger candidates — or those who share the same type of “name/history” baggage (e.g., Jeb!) — the prospect of sitting this one out is more appealing when Clinton is the likely opponent than if, say, Bernie Sanders or Lincoln Chafee were the likely nominee. (More on that in a second.)

In the end, of course, I am sure that Ted Cruz and John Kasich were “in it to win it,” but let’s be honest: Neither Cruz nor Kasich is (or at least was) really a nationally popular figure for the GOP.

In line with the argument forwarded by Banks and Kiewiet, these candidates and Trump were the last standing in the race for the GOP nomination because Clinton was such a strong contender. I will move on, but consider this: Why didn’t Paul Ryan, Mitt Romney, or Michael Bloomberg step into the race?
For the Democrats, the same argument can be applied easily to understand why Clinton’s competition for the nomination was so, well, weak. Regardless of how much you “feel the Bern,” it is essentially incontrovertible that he 1) is not a Democrat, 2) is nowhere near the mainstream politically, 3) had no national political presence, and 4) is not young.

To answer this question, you need to remember that a platform of “reduce inequality, make college free, create jobs, and tax the wealthy” is actually available to any candidate. Bernie’s platform is stock populism (not coincidentally like Trump’s, if one dares to claim that Trump has a platform).

Sanders was not the contender because of his platform; he had his platform because he was the contender. His platform includes a “plank” for Guam, for crying out loud! (No offense to Guam, but, for better or worse, it doesn’t have any electoral votes.)
Arguably, Sanders sought the nomination against Clinton precisely because this was his best opportunity and/or he couldn’t wait for a better opportunity. He built a platform, much as Trump has done with “walls” and “extreme vetting” based on the simple reality that Clinton, again, for better or worse, has a huge electoral advantage.
This advantage, to be clear, is at its heart “professional.” Clinton does not have the “right” (or the “wrong”) positions on issues. Rather, she has the political expertise and experience that makes other expert and experienced candidates think twice before pushing too hard to spend a lot of time fighting her in a general election.
You know, just like Banks and Kiewiet argued more than 25 years ago.