Two of the nation’s best pollsters have recently weighed in on the state of the Iowa Democratic race, with very different results. One subtle methodological choice might explain part of the difference, and on balance there is reason to think Bernie Sanders might be a bit stronger in one of the two polls than the topline result suggested.

The first Iowa survey was the one conducted by Ann Selzer and sponsored by The Des Moines Register and CNN. On Friday, it found Mr. Sanders with a three-point lead and 20 percent of the vote. Elizabeth Warren and Pete Buttigieg were at 17 percent and 16 percent. Joe Biden was in fourth, with 15 percent.

On Monday the other pollster, Monmouth, found Mr. Biden in first with 24 percent of the vote — nine points higher than in the Selzer poll. Mr. Sanders was in second, with 18 percent, while Mr. Buttigieg and Ms. Warren landed at 17 percent and 15 percent.

Either way, the race is close. Any of the four leading candidates could prevail, given the long history of late movement in Iowa caucus polling. In general, modest disagreements between polls ought to be expected, and it is no surprise that polls would frequently show different winners in a close four-way race like this one.