When it comes to assessing theories, political scientists like to talk about “tough tests” and “easy tests.” If a theory meets a tough test — that is to say, it works in an environment when other theories seem more viable — that’s a strong endorsement of the theory. For example, if a super-protectionist candidate was elected president and then supported ratification of a new trade agreement, that would be a tough test for the open-economy politics model.

If, on the other hand, a theory fails an “easy test”— one in which all the conditions for the theory to hold are at their most favorable — well, that’s a pretty powerful data point falsifying that theory. So if a super-free-trader was elected president but then rejected trade promotion authority granted to her from Congress, that would be a rejection on an easy test of presidential preferences mattering.

I bring this up because over at FiveThirtyEight, Nate Silver has written a long piece on what Donald Trump’s continued polling prowess means for “The Party Decides.” For the purposes of Spoiler Alerts, what matters is Silver’s paragraphs summing up this theory — in particular, what is meant by “party elites” or “party insiders.”

That’s really the bottom line: These people have some ability to influence the nomination, and they have some interest in doing so. That influence could take many forms, including holding a position of power, having access to a donor network, possessing scarce skills or knowledge, contributing time or money, or having the ability to persuade others through a media platform.
It might even be tempting to boil down “The Party Decides” to an idea like this: You ought to pay attention to what influential people who care about a party nomination are doing, since they can have a lot of say in the outcome. Indeed, that’s probably a better representation of “The Party Decides” than the idea that a monolithic establishment always wins.

Whether a Trump victory in the Republican primaries represents a clear falsification of the thesis is unclear. As Spoiler Alerts noted last Friday, it seems the party has decided it hates Ted Cruz more than anything else, which explains a lot of recent behavior. Furthermore, the establishment “lane” this cycle has stayed clogged up for the past four months. This has left Trump without a party-backed alternative. So while what’s happening is not good for “The Party Decides,” it’s not fatal either. So the GOP nomination fight in 2016 is not the easiest test of this hypothesis:

But let’s turn to the Democrats now, because that might be the easiest test of “The Party Decides” hypothesis you will find in the last 16 years. Consider the data:

  • In the endorsement primary among key office-holders, Hillary Clinton is leading Bernie Sanders by a score of 459 to 2;
  • Looking beyond office-holders, key Democratic interest groups like unions and Planned Parenthood and LGBT organizations have also backed Clinton, provoking some complaints from Sanders. To be sure, Sanders has done better here than with office holders, wining a few endorsements in this category, but Clinton has won way more;
  • Leading Democratic policy wonks and opinion leaders seem to strongly prefer Clinton over Sanders;
  • This week, President Obama went just about as far in endorsing Clinton as his successor as they could without explicitly endorsing her. Obama did so in a Politico interview with Glenn Thrush; as my Washington Post colleagues Greg Sargent and Chris Cillizza note, there is no way to read that interview as anything but tacit support for Clinton.  Obama’s advisers did the same thing in this Bloomberg story by Sahil Kapur.

If the “Party Decides” hypothesis is correct, then Clinton will be the nominee. It’s a very easy test of this theory.

Except that if you look at the Real Clear Politics averages for Iowa and New Hampshire, you discover that Clinton is in a real dogfight with Sanders. The polls in Iowa are very close, and FiveThirtyEight gives Sanders a better-than-two-thirds chance to win New Hampshire. It is certainly possible that Clinton could win the nomination even after losing both Iowa and New Hampshire, but it is also easy to envision Democratic primary voters bandwagoning with Sanders after two straight victories over the titular front-runner.

Now, Clinton is still (barely) leading in the aggregated polls in Iowa. FiveThirtyEight projects Clinton with an 80 percent chance of winning the caucuses. If Clinton wins Iowa, then the rest of her firewall should hold up. It would seem that the best comp for this race would be the 2000 Democratic primary. In that race, a front-runner with a long resume faced a pretty decent challenge from a more liberal senator, squeaked out a few narrow early victories, and then, ex post, won in a romp.

That would seem to be how this race plays out. But while everyone is focusing on what the GOP primary is doing to “The Party Decides” thesis, I’m just going to put this out there: If Clinton loses in Iowa and New Hampshire, then “The Party Decides” will have flunked the easiest test out there for the theory. Which will then require some serious navel-gazing among the political scientists in the room.