Many of the Trump folks believe that if they have a plurality of delegates, their man is entitled to the nomination. But that’s not really the way it has ever worked. The goal of a party convention is not to anoint the person who won more votes than anyone else in the primaries, but the person a majority of delegates think is the best nominee for the general election, and (not coincidentally) the one who has the fewest enemies within the party.
This has not really been an issue in the past 40 years or so, because the primaries usually end up coalescing around a particular candidate who unifies the party before the convention. This year, the candidate with the most delegates in the Republican primaries happens to be someone who is not (yet?) succeeding in unifying the party – and that’s why many more people than usual are working for, or hoping for, a contested convention. Mr. Trump can stave off this pressure – by winning primaries convincingly. If his support builds, he can make an argument for the nomination even if he hasn’t made it quite to the magic number of 1,237 delegates. But if his support weakens within the party in the next few weeks, and if he continues to fare poorly in polls against Hillary Clinton, it’s not at all unreasonable for Republicans to look for someone else at the convention.
I’m sure much of this is familiar to regular readers of this website. I mention it as prologue to a movie recommendation: of one of my all-time favorite films, The Best Man (1964). It’s the story of a contested convention, starring Henry Fonda and Cliff Robertson as the two chief rivals for their party’s nomination. There’s a lot of hardball maneuvering, not dissimilar to what we’ve seen so far this year. I won’t provide any spoilers concerning this highly suspenseful and entertaining film: It should be enjoyed as a straight-up thriller. I will say only that its remarkably serious point is that political parties have traditionally been a powerful force for compromise, among interest groups and ideologies. (This is no longer as true as it used to be, now that parties are more explicitly ideological. But it remains true to some extent.)
NB. The movie is based on a play by Gore Vidal, but there is very little of Vidal’s left-wing ideology in it. This is a movie not about policy ideas but about men and power – and it’s a darned good one. (There is some dispute about the final meaning of the phrase “the best man.” After watching the film, each viewer can decide for him- or herself whether the author meant that phrase ironically. My personal view is that he probably did – but that the film itself makes the case that the phrase is correct in a totally non-ironic sense.)