I ran an experiment in which I inserted a hypothetical South Carolina poll into our model in which Mr. Romney and Mr. Paul gained a couple of points from their previous polling average, while Mr. Gingrich, Mr. Santorum and Mr. Perry lost a point or two, and Mr. Huntsman held steady. Then I reran the numbers. The model gave Mr. Romney a much clearer chance of winning: 87 percent…

To reiterate, these are hypothetical numbers. But they’re consistent with what I’d expect to see if the New Hampshire bounce is typical, given what we know about how these things have behaved in the past.

But whatever the immediate effect from New Hampshire, there will be 10 full days of campaigning until the South Carolina primary on Saturday, Jan. 21. That’s a lot of time — nearly twice as long as the six full days of campaigning between Iowa and New Hampshire…

The problem is that there may be no Republican candidate poised to benefit from a downtrend in Mr. Romney’s favorability numbers.