[I didn't see David Weakliem and Andrew Gelman's related posts until after I wrote this. I plan to have a reply ready soon (tldr: I'm still skeptical). I'm also working on posts examining other aspects of the primary. "The polls" don't tell the whole story, but the rest of the details don't seem to tell that different a tale.]
The New York Times and company have been peddling a dangerous fantasy. It is easy to see the appeal of a scenario where the Republican Party suddenly comes to it senses and saves us from this threat to democracy, but based on all of the available data that would be all but impossible and encouraging people to hold on to that fantasy is as irresponsible as advising the debt-ridden to play the lottery.
I've been going through the polling for the last few presidential races. Joseph has been looking at things like ranked choice, and, as have many others, we both independently came to the conclusion that even before a single primary is run, unless something cataclysmic happens to the race, Donald Trump has basically won the nomination.
I'll see if I can get Joseph to talk more about the numbers that he has seen, but based on the historical record from places like 538 and Real Clear Politics, we are looking at an unprecedented level of support. Mitt Romney had what amounted to an insurmountable lead, but it was dwarfed by the level of support that Trump had in 2015, which in turn has been dwarfed by what he has now.
Barring truly unprecedented shifts in the way things have always worked, I can think of only three plausible scenarios where Trump fails to get the nomination. The first would be some kind of major health crisis. The next two would be based on big legal setbacks. Much of this hinges not on whether he is convicted but on where.
If Trump is convicted in federal court, he will go to a minimum security white collar facility where he will still be able to live a relatively cushy lifestyle while having access to the press and being able to play the martyr card. It would even be a fundraising opportunity. Just to show how far we have sunk, I'm not confident that this would be enough to cost him the nomination. Trump has apparently been thinking along these lines as well since there have been news reports of him asking questions like would he be able to have his own food sent in if he went to prison.
Georgia is a different story. As I understand it (and if there are any experts in the audience, please speak up) there is nothing analogous to Club Fed in the Georgia State Prison system. Though he would get some special treatment such as a secret service detail, this would be from his perspective very hard time and even if he were to be able to somehow win the presidency, he still couldn't pardon himself.
(There have been reports of Trump asking advisers what conditions in prison would be like. If he's been getting honest answers, Georgia has got to be making him nervous.)
The former president is the very definition of a flight risk. He has private planes, tons of cash, and lots of places to run to. Perhaps I am being insufficiently cynical, but I do believe that the GOP would dump Trump if he fled the country to avoid extradition.
Obviously these are extreme cases, and normally we wouldn't even bring them up, but as improbable as some people may claim them to be, a major health crisis or a criminal conviction are both far more likely than the possibility of anyone who is currently running or is likely to run in the GOP primary unseating a healthy, actively campaigning Trump.
There's one point we need to be really clear on, and it's something that political commentators have been doing a horrible job with over the past year. In normal times, anything that helps you win the nomination helps your overall chances of winning an election simply because without the first you can't have the second. That said, as savvy politicians like Richard Nixon have always understood, there are positions and actions that can improve your odds in the primary but seriously hurt you in the general. This has probably never been more true. Being sent to federal prison may actually improve polling numbers for the nomination, but they will almost certainly hurt November after next.