The FiveThirtyEight Team Goes To Iowa

DES MOINES — The new Des Moines Register poll conducted by Ann Selzer is now out on the Democratic side, and like the results for the Republicans released yesterday, it really doesn’t change our perception of the race. In the poll, Hillary Clinton is slightly ahead of Bernie Sanders, 42 percent to 40 percent, while Martin O’Malley brings up the rear at 4 percent. The FiveThirtyEight’s polls-only forecast continues to suggest that Iowa leans Clinton’s way. She’s still at a 66 percent chance to win, as she was last night, while Sanders retains a 34 percent chance. Clinton continues to lead in the model not only because the Selzer poll has her ahead, but also because Selzer’s polls have had a fairly significant house effect. That is, they have tended to produce better results for Sanders and worse results for Clinton than the average poll. The model takes that into account — if a pro-bernie poll is showing Clinton ahead, the model thinks she must really be ahead. In the FiveThirtyEight polls-plus forecast, Clinton maintains a larger advantage. She’s at an 82 percent chance to win, while Sanders is at 18 percent. Clinton is in a better position in this forecast because of the many endorsements she’s earned. Moreover, Sanders didn’t really rise from the 39 percent he earned in the last Selzer poll, rather, Clinton dropped from 48 percent. Support from within her party’s infrastructure may help push newly undecided voters back into her column. For now, the race for Iowa remains close on the Democratic side with two well-liked candidates earning favorable ratings above 85 percent from Democratic caucus-goers. Don’t be surprised if a number of voters change their mind in the final weeks of the campaign.