How the pollsters got Iowa wrong

Of the polls conducted by live telephone interviewers, only one survey – from Quinnipiac University – was in the field all the way until Caucus Day. But that poll, which showed Trump with a 7-point lead, was conducted over the course of an entire week.

The second-newest poll was the Des Moines Register survey, conducted by Iowa polling legend J. Ann Selzer. But that poll was conducted last Tuesday through Friday, meaning it also may have missed any late movement.

The entrance poll suggests those late deciders went to Cruz and Marco Rubio. Rubio won 30 percent of these voters, and Cruz captured another quarter. Just 14 percent of those who decided in the final days backed Trump.

The last few days in Iowa may have been consequential: Trump skipped the Fox News Channel debate in Des Moines last Thursday. While his threat to boycott the gathering began earlier in the week, that means just one of the four nights of interviews in the Des Moines Register poll were conducted after the debate, for example.