The most accurate Iowa Democratic poll has just come out!

The recent track record of her firm, Selzer & Company, is impressive: Selzer, who has polled for the Des Moines Register for decades, was the only pollster to nail the order of Democratic candidates in 2004. Her final poll before the 2008 caucuses accurately predicted that a surge of first-time caucusgoers would propel Barack Obama to a decisive victory. Selzer saw former Pennsylvania Sen. Rick Santorum’s surge in the waning days before the 2012 GOP caucuses when few others did.
And just last year, the final Register poll in the Iowa Senate race showed Republican Joni Ernst with a 7-point lead, contrary to other polls that showed a much closer race with Democrat Bruce Braley. Braley’s campaign decried the poll, calling it an “outlier.” But Ernst won by 9 points.

That’s not to say the Des Moines Register poll is perfect. It sometimes misses on a candidate by a lot. Selzer’s final poll in 1988 missed Republican Pat Robertson’s eventual vote share by just more than 10 percentage points. Same thing with Kerry in 2004.3

Who might benefit from that type of miss this time around? History suggests there are two types of candidates who tend to outperform their polls. The first is a candidate who does well among Christian conservatives. Selzer’s final polls on the Republican side in 1988, 1996 and 2012 all missed the candidate favored by Christian conservatives by at least 8.5 percentage points. That could be good news for Cruz. Secondly, candidates with late momentum, such as Kerry in 2004 and Santorum in 2012, also tend to beat their polls. That could be beneficial to Rubio, who seems to be gaining in some polls.

Could there also be a big error on the Democratic side? It’s possible, but Selzer did particularly well in 2000, the last Democratic campaign with only a few candidates running. Fewer candidates means voters have an easier time settling on one candidate and reallocation of support becomes less of an issue.

Of course, we won’t know how accurate Selzer’s final poll is this year until Monday or the day after. It’s worth remembering, however, that even the best pollsters — and Selzer is one of the best — aren’t perfect.

“I will take the Des Moines Register poll, which is the gold standard for polls in Iowa,”

-Bernie Sanders