Donald Trump beats Marco Rubio in a head-to-head matchup among Republicans

In my conversation with political scientist Alan Abramowitz, we spent a fair amount of time discussing whether elite confidence in Marco Rubio is justified. This morning, Abramowitz pointed me to a new Economist/YouGov poll that suggests maybe it isn’t.

One way of downplaying Trump’s persistent dominance in the polls is to suggest his 20-30 percent is a ceiling, not a floor. Nate Silver, for instance, wrote that Trump “has 25 to 30 percent of the vote in polls among the roughly 25 percent of Americans who identify as Republican. (That’s something like 6 to 8 percent of the electorate overall, or about the same share of people who think the Apollo moon landings were faked.)”

The idea here is that Trump’s lead represents a fractured field: As weaker candidates drop out and the establishment consolidates around a single anti-Trump, that candidate will pass Trump in support even if Trump holds his current numbers.

But in a head-to-head matchup among Republican voters, Trump beats Rubio 57-43. That suggests that Trump’s ceiling, at least among Republicans, is far above his current 25 to 30 percent, and he may well benefit as weaker candidates drop out.

One response to this might be that voters will, in the coming months, learn something about Trump that will change their minds and vault Rubio ahead in this competition — that has happened, after all, to many other frontrunners. But while that’s clearly possible, it’s also getting harder and harder to imagine what it is voters could learn about Trump at this point that would shock them.

Meanwhile, there are things Republican voters might learn about Rubio — like his immigration record or his reliance on dark money — that could undermine support for him, too.

Trump may beat Rubio in a head-to-head matchup, but what if Trump drops out? And what if Carson drops out?

This question tests something interesting: Do GOP voters like Trump and Carson because they’re uniquely compelling candidates? If so, they may well see Rubio as the next most compelling candidate, even though he is pretty stylistically and substantively different. But another possibility is that Republicans like Trump and Carson because they’re combative, outsider conservatives with hard-line positions on key issues, in which case Rubio — a genial establishment favorite who has a real record of working with Democrats — probably isn’t a fit.

The results here suggest the latter. Of the candidates in the race, Cruz is closest to Trump and Carson in ideology and approach, and it looks like he is the main beneficiary if they drop out of the race.

One possible argument for Rubio is that though he may not be many voters’ first choice, he could prove to be a lot of people’s second choice, and so his strength will reveal itself as other candidates prove unacceptable or drop out.

At the moment, though, there’s relatively little evidence of that: Rubio and Trump are within a percentage point of each other when it comes to voters’ second choice, and Ted Cruz and Ben Carson are ahead of both of them.

None of this means Rubio is cooked. It’s only to say that for all that the conventional wisdom and the betting markets favor Rubio, it is really hard to find support for his strength in the numbers.