NATE SILVER, I HAVE A FEW QUIBBLES

Political writers who put all their faith in data or poli sci keep telling us that there's absolutely zero chance of success for Donald Trump once voting actually starts in the primaries and caucuses. I think that's probably true, although I've identified several bubble-destroying moments for Trump that never did any real damage. So I admit I know nothing. Nate Silver, however, is far more confident in his own prognostication skills, so he gives us five reasons why it's all over but the deflating for Trump's bubble:

... the problem isn’t just that the national polls at this stage in the race lack empirical power to predict the nomination; it’s also that they describe a fiction. I don’t mean to suggest that Donald Trump’s support in the polls is “fake.” I have no doubt that some people really love him or that he’d be the favorite if you held a national, winner-take-all Republican primary tomorrow. However, the “election” these polls describe is hypothetical in at least five ways:

* They contemplate a vote today, but we’re currently 174 days from the Iowa caucuses.

* They contemplate a national primary, but states vote one at a time or in small groups.

* They contemplate a race with 17 candidates, but several candidates will drop out before Iowa and several more will drop out before the other states vote.

* They contemplate a winner-take-all vote, but most states are not winner-take-all.

* They contemplate a vote among all Republican-leaning registered voters or adults, but in fact only a small fraction of them will turn out for primaries and caucuses.

Sounds sensible -- but point #3, at least, is probably wrong, as Politico reports, because of our brave new campaign finance world:

... unlike previous cycles, the tiering of the 2016 Republican presidential field appears unlikely to result in the quick exit of the GOP laggards. That’s because each is the beneficiary of super PACs that in many cases have raised orders of magnitude more than the campaigns themselves. The PACs, in effect, become a bridge to viability, sustaining struggling candidates....

“I don’t think there’s any incentive to drop out as long as you can put gas in the truck and there’s PAC money out there,” said Sam Clovis, an Iowa adviser to the Perry campaign, who said Perry’s as upbeat about his chances as ever. “There will be some adjustments -- but again, it’s just a matter of resetting the stride.”

... Perry’s not the only candidate subsisting on support from his super PAC. Paul’s campaign has been the beneficiary of a super PAC-funded ground game in Iowa.

... As for Santorum, the 2012 Republican runner-up who has largely scraped along at the bottom of GOP polls this year has adopted a different posture than other longshots. The organization is preparing to announce a string of hires this month, including five paid staffers in Iowa and additional staff in New Hampshire. His super PAC is helping carry the load....

I don't know when the obvious losers are going to drop out. The ones with generous sugar daddies may stay in it for a dozen contests or more.

Yes, I know that the GOP requires every state with a contest before March 15 to distribute delegates proportionally. After that, it's winner take all. The way that's supposed to work is that struggling candidates are supposed to drop out early and leave only a couple of contenders standing -- at which point the strongest candidate should start gobbling up all the delegates in every late state, winning as the consensus choice by majority vote. (Read: Jeb Bush.)

But what if half a dozen or more of these delusional SOBs refuse to withdraw? What if that makes it possible for the much-disliked Trump to be the victor in winner-take-all contests with the vote of a fervid minority?

Remember, there could be a lot of candidates doing well in some states and not others. Walker's strong in Iowa. Kasich is suddenly doing well in New Hampshire. Graham, until recently, was in double digits in his home state of South Carolina. Rubio does okay in Florida. What if they all stay in, plus Cruz, Paul (who might show his father's strength in caucus states), Carson (who might overperform in Jesusy states) and who knows who else? (Well-heeled Fiorina? Wall Street-funded Christie?) The field could still be, to use the worn-out metaphor, a clown car as we enter spring.

Now a word on point #5: It's assumed that Trump's voters aren't likely voters. By standard poli-sci definitions, they probably aren't. But what if Trump sustains this crazy fever and they're highly motivated voters? That's how Jesse Ventura got elected governor, after all -- not by turning out likely voters but by inspiring new voters to show up at the polls.

Yes, Ventura benefited greatly from same-day registration in Minnesota. Trump will need to win states where he won't have that advantage. And it's really hard to imagine him putting together a serious voter-registration or get-out-the-vote effort.

But what if the whole thing goes pear-shaped? Are we sure something insane couldn't possibly happen? How can we be absolutely certain about predictions with a field this huge and campaign financing this lavish, given that we've never dealt with a similar set of circumstances?