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So what happens after Donald Trump and Ben Carson?

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Donald Trump has led the Republican field for president for 88 days, as of Wednesday. It's a statement that many people would never have expected to be true, and yet it is. It's like Matt Novak's long-running Twitter joke counting down to Trump's inauguration. When Novak started the gag, 100 days ago, Trump was way back in the pack. With each day Novak has counted down, the prospect of it coming true has apparently gone up.

Until recently. On Tuesday, while the political world was gearing up for the first Democratic presidential debate, Fox News dropped a new poll of the Republican field. The short version of the story is that the status quo was maintained: Trump first, Ben Carson second, and so on down the list.

The longer version, as longer versions tend to be, is more interesting. Trump's lead over Carson was only one percentage point — the smallest lead Trump has seen in Fox polling and down from an eight-point lead in September. Trump didn't fall; Carson gained.We can step back and look at the Real Clear Politics polling average to see that this fits into a longer trend.

Even as Trump's support has hit a new plateau, his lead is dropping thanks to Carson's improvement.

Beyond those two, not much has changed. Carly Fiorina, who was expected to be part of the top-three conversation, hasn't kept up her rapid post-debate growth. Jeb Bush saw a bump, but then slid downward again.

I am now going to say something controversial that will result in mean e-mails from people: Few experienced political observers think that either Trump or Carson will be the party's nominee. That's at odds with a lot of voters, mind you. A recent CBS poll suggested that Republican primary voters rank Trump and Carson first and second in having the best shot at winning a general election next year — meaning that people are confident that they're acceptable nominees.

Why do experts disagree? In part because experts like to have opinions on things, myself included. But also in part because past nominees haven't looked or acted like Trump and Carson. They have had experience in elected office and have racked up endorsements from established politicians. They have the backing of big donors. That sort of thing. And also because we saw candidates like Carson and Trump (to at least some extent) surge in 2012, only to once again recede.

But if you think Trump and Carson won't make it across the finish line, it raises the question of who will.

Fox also asked people who they'd back in the Republican primary as a second choice. The poll outlines how each candidate would do without Trump, Carson and Bush in the race, allowing us to see the effect of one of those three dropping out.

If we look at the gain in the polls from each one dropping out, it looks like this.

If Trump drops out, much of his support goes to Carson. (And, super weirdly, some to Jim Gilmore?) If Carson drops out, a lot of his support goes to Trump. Fiorina picks up some support if Carson drops out, but not if Trump does. (If Bush drops out, his not-huge base of support goes in random directions.)

The summary here is that there is fairly substantial overlap in the bases of support for Carson and Trump. So if both eventually drop out, it's hard to anticipate where their support would go. (Of course, if they do drop out, it's because those bases of support have likely already eroded to other candidates, but that's another subject.) Would Trump-Carsonites be happy with Marco Rubio? Would they migrate over to Fiorina? Where does that base go?

One of two things will happen: The first is that Trump or Carson will win the nomination, once again proving those idiot experts wrong. The other is that Trump's lead will finally vanish in a blink and Carson's will at some point thereafter. The field will evolve and the issues will shift. And voters who now back Trump or Carson will become voters who, like so many voters before, briefly dallied with glamorous rebels before settling down to marry a politician with a lot of money and endorsements.

Only a fool would use the data at hand try to predict which politician that will be. A fool, or an expert.