No new candidate is going to jump in late and win the Republican presidential nomination. It’s not going to happen. It’s been too late for months, and it’s too late now. Really.

I thought Josh Putnam had killed this off after Rhodes Cook reopened it, but with Nate Silver weighing in, I guess not. So, here goes, a long, long, long look at why the field is set.

The main focus of Silver’s piece is, as he says, is about how the current structure of public opinion leaves a strong opening for a new candidate, as opposed to the process argument that Cook made. And he’s right that right now, there does appear to be a large, and perhaps a huge, opening for another candidate. We know the story of this…most of the candidates are not particularly well liked (by Republicans). Silver looks at the Gallup poll asking which candidates are acceptable, and notes that only two, Gingrich and Romney, have a net positive acceptability, and it’s certainly not hard to picture either of them with a deteriorating image as the campaign goes along.

And yet what makes this kind of thinking not work out is that process matters, and it matters in a way that works to produce a candidate who is popular within the party. Moreover, process matters too for the chances that any candidate will jump in late.

OK, let’s get to it.

First of all, the support registering in the polls so far appears to be very soft. In my view, that probably applies to the “Not Acceptable” numbers that Silver touts in every case except for Ron Paul. If one of the others, especially Rick Perry, could manage to put together a solid week, chances are that “Not Acceptable” number would melt away. After all, right now those numbers are much higher than the “unfavorable” ratings for each candidate. Sure, it makes sense that a substantial group of Republicans might like Michele Bachmann but still find her unacceptable as a presidential candidate, but overall I’m not prepared to put too much weight on that single poll. If I’m right about that, then if both Romney and Gingrich collapse soon one of the other candidates could wind up winning; it wouldn’t be necessary to bring in someone new. So Silver’s “motive” argument, in my view, falls short.

Not to mention that there’s really no one out there with the heft to overshadow the rest of the field with a late entry. Mitch Daniels, John Thune, even Jeb Bush: none of them have the clout and reputation to immediately swoop in and dominate the party on their own merits.

For the rest, one needs to turn from public opinion back to process.

Suppose a new candidate announced today? Well, as Cook acknowledges in his column, filing deadlines are already upon us. In fact, and using his numbers, filing deadlines have passed in states with 339 delegates. The window closes on another 155 on Thursday, and 49 more on December 22. Miss all of that, and you’re spotting the field 543 out of 2264 total delegates. That’s a huge, huge hole to begin from if you hope to get a majority; after all, it’s not as if it’s all that likely that a Mitch Daniels or a Paul Ryan would sweep the rest of the states, even if everything went very well. And another avalanche of filing deadlines show up right after New Year’s, with another 342 in the first half of January. So wait until the field sorts itself out after New Hampshire, and over a third of the delegates are gone.

So a new candidate who came in right now would start behind in the delegate count, and scramble to put together a viable campaign while the current candidates were busy organizing and campaigning. He or she could compete in Iowa (but without any organization at all), but even an improbable win there would be followed by…nothing. The other candidates would then compete in a series of primaries in which Bush or Christie or Daniels would at best get some write-in votes. Moreover, the field will winnow after Iowa (and winnow even more if an outsider just won it!). Think about it: imagine a Christie/Gingrich/Paul finish in Iowa. Guess what? Only those three and Romney, at best, go to New Hampshire, but Christie isn’t on the ballot, so one of the other three wins. If it’s not Romney, he drops out, and suddenly Newt Gingrich is the only non-Paul candidate on the ballot and still running in a whole series of states, piling up the delegates. Or, Romney wins, and the Gingrich bubble pops after his shocking Iowa loss, leading to Romney building a large delegate lead before finally reaches the ballot in (some of the) Supertuesday states in March.

Later entries are even less likely to work. Silver spins out a scenario in which Newt wins in Iowa, does well in New Hampshire, and then wins both South Carolina and Florida, despite party leaders wishing for another option — and so a new candidate is recruited then. That matches Cook’s idea of a February entry, again after the Florida primary on January 31. But the math is even more impossible that way. An entry in the first week of February would have no shot at the 883 delegates accounted for above, plus another 95 with late January deadlines, or the 156 selected in early caucus states. That’s about half of the total number of delegates. And surely Romney would drop out if that was happening, meaning that Gingrich would likely sweep most of the delegates available, with Ron Paul the only active alternative on the ballot. Newt, who would be popular enough to have won all those early contested events, would only have to win a small percentage of the remaining delegates to clinch the nomination.

Look, if Ronald Reagan 1979 (or the Democratic version, Ted Kennedy 1979) was lurking out there…well, you could try to find ways for that candidate to grab enough delegates through write-ins or other such desperation plays to survive until he was on the ballot — although Kennedy’s actual story is a great caution to the grass-is-greener aspect of all of this. That’s not Chris Christie or Mitch Daniels. There aren’t waves of ordinary Republican voters eager to hear how they can vote for Bachmann so that it will count for Paul Ryan, or some similar work-around.

So a late entry doesn’t work.

Next stop? The deadlocked convention. Could a candidate jump in there and win it?

Nope. It’s not just that it doesn’t happen; it’s that there’s good procedural reasons that it (almost) can’t.

What a deadlocked convention needs is three or more candidates winning delegates. But the nature of the process is that candidates who do poorly in the first states are starved for resources and drop out. That’s already happened with (at least) Tim Pawlenty. It will happen in the next month with, almost certainly, any candidate who does badly in Iowa and New Hampshire…most likely, we’ll be down to three or four active candidates at most, one of whom will be Ron Paul. It’s highly unlikely that we’ll still have more than two plus Paul after Florida — we did, briefly in 2008 (with Huck, Mitt, and McCain all making it to Supertuesday), but the logic of the process makes that the best-case scenario for a split field, and as we saw in 2008 it wasn’t really all that split.

Meanwhile, Paul is unlikely to pile up very many delegates. There are just too many events that are winner-take-all, either by state or congressional district, for a candidate who gets a consistent 15 percent everywhere to have that translated into very much at the convention. My best guess is that Paul will be very challenged to reach 10 percent of the delegate total as a very optimistic upside.

Which means that if there are only two other candidates in most states that they’ll have to finish in a dead heat for Paul’s handful of delegates and the smattering of delegates won by candidates who drop out early to prevent the winner from hitting 50 percent + 1.

I should include one caveat…of course there is a non-zero chance of the current field not producing the nominee. If someone wraps up the nomination early on, and then falters in some extraordinary way, then of course one can construct a scenario…call that the meteor hits the debate hall caveat. Don’t think, however, that a normal but severe campaign gaffe could disrupt a previously settled nomination. Remember: the convention is self-governing. The convention is its delegates. And the delegates chosen are the ones slated by the candidates, and therefore those chosen to be delegates are normally the most fanatical supporters of the candidate that can be found. They’re going to be the first to rationalize or ignore any new negative information about their hero, and the last to accept it. What that means is that anything that isn’t strong enough to knock out a presumptive nominee altogether isn’t very likely at all to lead to a revolt by the convention. So, sure, if Gingrich switches wives or religions again between winning the last primaries and when the gavel drops in the convention, or if one of the others staggers over the finish line with 60 percent of the delegates and then develops a health issue, well, then things open up.

But don’t think that party leaders can take a nomination away from someone who has won it in the primaries and caucuses. There’s just no mechanism for doing it, no matter how much they might want to.

The actual dynamic if an unpopular candidate wins the nomination in the spring is that we’ll have a month or two of serious buyer’s remorse and lots of improbable ideas hatched on how to overturn it…followed by a few months of GOP elites finding new strengths in the nominee and the rank-and-file falling in line. Republicans will get all excited about the VP pick, and with the competition out of the way they’ll start remembering that their real target is Barack Obama. By the time the convention opens, they’ll be as excited about their ticket as Democrats were in 1992 or Republicans were in 2008.

As regular readers know, I don’t expect Newt Gingrich to remain the polling leader into the spring and sweep all the states in which he currently holds a polling lead. But should he do so? If Newtmentum continues through Supertuesday and he wins most or all of the states that day, he would be the nominee. End of story.

Far more likely is that party actors now rally around Romney — or, perhaps, Rick Perry, if he can avoid damaging himself for a week and starts converting his cash advantage into a polling bump.

Either way, however, the field is going to winnow, and my guess is that it’ll be all over within six weeks. Or, perhaps, it will drag out to March. Either way, the field is set, there’s not going to be a deadlocked convention, and one of the current candidates is going to be the Republican nominee.

[Cross-posted at A plain blog about politics]

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Jonathan Bernstein is a political scientist who writes about American politics, especially the presidency, Congress, parties, and elections.