Via Breitbart, I can definitely see him winning Iowa, which would all but finish off Scott Walker. I can also kinda sorta see him winning the general election if everything broke right for him — scandals blow up what’s left of Hillary’s trustworthiness, black voters stay home with Obama off the ticket, GOP establishmentarians grudgingly stick with Trump in the name of reclaiming some leverage over the White House, and Trump’s platform (including/especially on immigration) peels off enough centrist Democrats to more than make up for the number of Republicans who can’t stand Trump and decide to stay home. The part I have the most trouble with here is seeing how he wins the nomination in the first place. This field inevitably will winnow after Florida to three or four plausible candidates at most. After the “SEC primary” on March 1, it should winnow even further, possibly leaving two or three candidates left standing. If Trump’s one of them, pressure on GOP voters to unite behind the other guy (or, if there’s more than one alternative to Trump left, to pick one and unite behind him) on ideological grounds and electability grounds will be tremendous. At some point, barring something very unusual happening, a long Trump run will turn this into a “Trump versus Not Trump” race. And there’s no reason, with this guy hovering at around 25-30 percent in the polls, to think that most of the remaining 70-75 percent of Republicans won’t line up behind “Not Trump.” In fact, because Trump insists on insulting everyone else in the field, hard feelings may ensure that even candidates who aren’t fans of one another might band together to stop him if it comes to that.

Trump’s path requires, I think, at least two other rivals stubbornly deciding to continue the race, dividing the “Not Trump” vote between them, well into the spring despite Trump-haters from across the party howling at one of them to step aside and endorse the other. Paint me a picture of how that happens. Realistically, if Trump were to hang around until the SEC primary, he’d need to have won one or more of the early states. If he wins Iowa, as Halperin suggests here, that almost certainly means Scott Walker will flame out of the race quickly. Florida could also eliminate either Jeb Bush or Marco Rubio (or both, if Trump were to upset them there). So who’s still viable realistically once the “SEC primaries” are held? Trump, the Florida winner, the New Hampshire winner, and probably Ted Cruz, who’s banking on the southern states to be a launching pad for him nationally. At that point in the race, with the field effectively down to four candidates maximum, how many Trump-supporting conservatives will think hard about their choices and decide Cruz is a better bet against Hillary than the volatile, not-terribly conservative Trump? How many Trump-supporting moderates will think hard about their choices and decide Rubio or Bush or Kasich (whichever one is left) is a better, more electable choice for the general than Trump? In fact, the more I think about it, the more I wonder if there isn’t a deeper strategy to Ted Cruz’s scrupulous cordiality towards Trump. Everyone assumes Cruz is being nice to him because he expects to inherit Trump’s righty supporters at some point (which is no doubt true), but Trump may also be valuable to Cruz as a guy who can block and tackle for him in the early states. Cruz can survive losing Iowa but I’m not sure Walker, the Iowa native and regional governor, can. At this point Trump may have a better shot at taking Walker out than Cruz does. Once Walker’s gone, his evangelical and tea-party voters may slide over to Cruz in time for the SEC primary, at which point other undecided righties will likely be looking for an alternative to Trump as the race gets serious. Cruz would be well positioned to pick up their support.

And what if three or four candidates do hang around all the way to the convention next summer, as Sean Trende imagined might happen? With the GOP establishment in an uproar demanding that Trump not be nominated, party chieftains would intervene and try to broker a deal among the remaining candidates to form a ticket themselves and deny Trump the nomination. The only way they might not be able to deny Trump is if he finished with a near-majority of delegates, such that leaving him off the ticket would feel like cheating and infuriate his fans into staying home in the general election. Even then, though, they’d probably try to exclude him. And even if Trump ended up as nominee, the hardened anti-Trumpers supporting other candidates might well decide to stay home in protest themselves, making his task even harder. Long story short, the longer Trump runs and the more polarizing he is, the less likely it is that the party will unite no matter who the eventual nominee is. If you’re a Trump fan and want to see him nominated, your best — and probably only — chance is for him to shock the world by running the table early and winning Iowa, New Hampshire, and South Carolina so that he builds up irresistible momentum … at which point Mitt Romney will be drafted to try to stop Trump at the eleventh hour after all.