His argument is as follows: One popular theory of presidential nominations, which we can call the "Party Decides" theory after the book that introduced it, holds that nomination outcomes are the product of elite coordination. According to this theory, party elected officials and interest group leaders identify a candidate during the "invisible primary" period before Iowa and New Hampshire whom they view as both loyal to their policy priorities and electable in a general election. These elites steer endorsements, money, and other resources to the candidate, who therefore enjoys a prohibitive advantage in the nomination race. Party voters ostensibly hold the power to decide nominations via the primary process, but are in fact ratifying the choice already made for them by the party leadership.
Drezner says this theory "seemed to explain nomination fights of the recent past quite well." I disagree with that assessment, but nobody denies that Trump's current ascendancy represents a serious challenge to the theory's validity in 2016. Drezner argues that the theory's very success might have paved the way for Trump by lulling party leaders into complacency about his inevitable defeat, which has left them ill-equipped to stop him now that we're a week away from Super Tuesday. In other words, the very act of publishing an analysis of party nominations has implicated political scientists in its apparent real-time refutation—a conclusion judged "surprisingly plausible" by Matthew Yglesias of Vox.
I don't find it plausible. Among the reasons why:
1. You don't need to believe that "The Party Decides" in order to have deemed Trump an unlikely nominee up until a few weeks ago. (I know because I don't, and I did.) Trump's candidacy is more or less without precedent in modern politics, and given the well-documented instability and lack of predictive power of pre-nomination polling, there was little reason for anyone to believe based on previous experience that a candidate with his profile would sustain his lead from last summer and fall into the early stages of the nomination season itself. Those who predicted Trump's demise did not necessarily assume that it would occur due to the united opposition of Republican elites; many pundits—and, no doubt, politicians—concluded that he would lose attractiveness to the electorate as he was subjected to more scrutiny and citizens became more serious about making up their minds. Alternatively, commentators expected that Republican voters, again with some justification, would reject Trump once they learned about his previous non-conservative issue positions and support for Democratic candidates.
2. Drezner says that "Even as the media covered Trump, even as late as the South Carolina debate, pundits were also talking about how his latest transgressive comment would doom his chances." True, but that's because Trump's remarks (such as blaming George W. Bush for failing to stop 9/11) were thought to be likely to offend Republican voters, not Republican leaders.
3. More broadly, Drezner implies that the Party Decides theory has become so well-established as to constitute the conventional wisdom among media commentators. I don't see that. Specialized explainer sites like Vox and FiveThirtyEight have certainly proven sympathetic to the PD argument, but my own sense of the more general type of punditry one would find on CNN, for example, subscribes to a view of nominations that emphasizes candidate strategy, voter preferences, and electoral "momentum"; endorsements and other forms of elite behavior are deemed to matter but are hardly predictive by themselves.
4. Drezner suggests that Republican elites' view of the nomination process has been formed primarily by reading "smart take after smart take" in the press. I doubt very much that this is generally true. More likely, Republican leaders do not perceive themselves as holding determinative power over nomination politics. Instead, they are scared to death of a popular base that they do not fully understand and struggle mightily to satisfy. In a world in which the Majority Leader of the House can be defeated in a Republican primary election after outspending a virtual nobody by 25-to-1, I doubt that Republican officials view the contemporary nomination process as a system that reliably bends to their will even if they do attempt to exercise control over it.
Trump has broken so many iron laws of politics in this campaign that we need to think about the implications of his candidacy for many different facets of the political world, and try to sort out how much of the Trump phenomenon represents a deeper change in the way American politics works. But we should be careful about assuming that a Trump nomination, if it occurs, necessarily represents a failure of The Party to Decide soon enough or decisively enough. Perhaps Trump is simply illustrating the fact that there is no The Party with the power to Decide in the first place.