Those of us who argue that political parties, rather than the American voters, are decisive in choosing presidential nominees are being challenged. Most recently, Vox's Andrew Prokop has said that voters have the upper hand in some cases.
As I read the evidence, however, the party has chosen each nominee since the 1980s. So let's look at how a nomination battle really unfolds.
As party actors approach a presidential election, they have many possible goals: They may care about winning the general election; about making sure the nominee is committed to their priorities; or about being close to the (potential) president.
Candidates announce. Some are well-known with clear records; others not so much. Even those with long track records may not have public positions on issues important to this or that group within the party. Presidential nominations define the party, so a complex game proceeds of simultaneously fighting over its agenda while also binding candidates to that platform.
Those who care about winning the general election look for clues about how candidates -- most of whom have never run campaigns outside of their home states -- will do on the national stage.
These political leaders, organizers, donors, professionals and activists have a strong interest in communicating their choices to one another. They do this through endorsements, campaign donations and media statements; or by signing on to candidates' staff and advisory committees; or simply in conversation with those close to them in the party network.
Sometimes, the party has settled on a contender before the first voters head for caucuses in Iowa. A clear-cut example was in 2000, when Democrats quickly chose Al Gore and Republicans rallied around George W. Bush.
Yet sometimes these dealings take longer. The people making the decision may wait for assurance that a possible nominee is sufficiently committed to the party agenda. Or they may have questions about a contender's general-election prospects, and use the caucuses and primaries to test him or her.
Prokop sees those cases as proof that the party doesn't decide (he includes as examples the Democrats in 1988, 2004 and 2008, and the Republicans in 2008). But the parties were just waiting -- a very different thing.
Take, for example, the Democratic nomination battle in 2004. Several plausible candidates ran. None were obvious choices. So party actors waited. As Howard Dean rallied in the polls and showed signs of potentially impressive grass-roots support, many were intrigued. The surge by the obscure former governor of Vermont was, news reports suggested, fueled by fancy new internet campaigning. Perhaps he had unlocked some electoral magic? If so, and since he supported party orthodoxy on most issues, perhaps he would have been acceptable. But when Dean failed to produce results in Iowa, party leaders immediately abandoned him and rallied around John Kerry, who impressed them with a victory out of his region.
In 2008, when Mike Huckabee won the Iowa caucuses, Republican leaders didn't swarm to him the way Democrats did to Kerry in 2004, because he wasn't acceptable to important party groups. Similarly, impressive showings by Paul Tsongas in New Hampshire in 1992 and Jesse Jackson in several states in 1988 and Rick Santorum in Iowa in 2012 didn't win them much.
The only contest after 1980 in which the party didn't exactly choose appears to be the epic Hillary Clinton-Barack Obama contest in 2008. In that case, Clinton began with more party support (as Prokop notes, John Edwards had more endorsements before Iowa than Obama did). Obama was interesting to many party leaders, but they wanted a sign that he could do well nationally. After he demonstrated he could capture white votes by winning Iowa, he rapidly picked up support. That part is about voters providing evidence to party actors, not about voters choosing a nominee. After that, however, since both he and Clinton were acceptable to the party and fully committed to its agenda but party actors remained split over their preferences, they let the voters make the final call. That was a party win, not a party loss.
If the past is a guide, Republican party actors will not only be able to defeat Donald Trump or Ben Carson; they will also likely choose from among those they like. Perhaps they'll do that in the next several weeks, or perhaps they'll wait until the early states provide new evidence about who is electable. That they haven't chosen - yet - between Marco Rubio and Jeb Bush, and possibly among a few others, doesn't mean they won't do so. And if they wait to use information from what voters do in early states, that doesn't mean that those events will pick the nominee.
Jonathan Bernstein is a Bloomberg View columnist covering U.S. politics.