Marco Rubio finished in third in Iowa — a “strong third” in which he outperformed his polls, but third nevertheless. And yet, his chances of winning the Republican nomination nearly doubled according to the bookmaker Betfair, from about 30 percent before the Iowa caucuses to 55 percent now.

Meanwhile, Donald Trump, who finished ahead of Rubio although behind Ted Cruz, saw his chances halved from 50 percent to 25 percent.

Even if you acknowledge the importance of the “expectations game,” isn’t that a little excessive? Well, maybe.

But I think Betfair is coming up with approximately the right answer.

Here’s why: Presidential nominations are a lot like the stock market. In the long run, they’re reasonably well governed by the fundamentals. In the short run, they can be crazy. Iowa represented the equivalent of a stock market correction, a sign that sanity might prevail after all.