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Our Final Forecast For The Iowa Caucuses

With just a few hours to go before the voting starts in Iowa, it’s time for us to freeze the FiveThirtyEight primary forecast model! So here are our final estimates of each candidate’s chance of winning a majority of pledged delegates and their chances of winning Iowa ahead of tonight’s vote.

First, our overall forecast continues to view former Vice President Joe Biden as the candidate most likely to capture a majority of pledged delegates, with a roughly 2 in 5 (43 percent) chance overall. But the other candidate making a case for the “front-runner” label, Sen. Bernie Sanders, isn’t too far behind. Sanders currently has a 3 in 10 shot of winning a majority. No other candidate has better than a 10 percent chance, with Sen. Elizabeth Warren at 5 percent and former South Bend, Indiana, Mayor Pete Buttigieg at 4 percent. In fact, there is a higher chance that no single candidate wins a delegate majority by the time voting ends on June 6 — the model gives that outcome about a 1 in 6 (17 percent) shot of happening.

final forecast before iowa

But tonight, the focus will be on Iowa, so let’s turn to the forecast’s outlook for the Hawkeye State and the final batch of Iowa polls that dropped over the weekend. Coming into the caucuses, uncertainty is the name of the game, so readers should be ready for a wide range of outcomes. Sanders is a slight favorite, with a 2 in 5 chance (41 percent) of winning the most votes, while Biden has a 1 in 3 (32 percent) shot of winning. Buttigieg and Warren aren’t too far off, though, at 14 percent and 10 percent, respectively, while Sen. Amy Klobuchar also has a 2 percent shot. Taken together, these figures suggest the race in Iowa is still pretty wide open.

We wish we had more polls going into Iowa — in particular the last big Des Moines Register poll — so we could have a better sense of any last-minute movement in the race. But looking at the four new polls we do have, Sanders’s chances have improved from 36 percent Friday to 41 percent as of 3 p.m. Monday. (Biden’s chances ticked down from 36 percent to 32 percent while Buttigieg’s and Warren’s odds are largely unchanged.) Here’s a quick look at the last four surveys of Iowa released on Sunday and earlier today:

  • On Sunday, Data for Progress and Civiqs found Sanders leading by 7 percentage points over Warren, 28 percent to 21 percent, with Biden and Buttigieg tied at 15 percent. Civiqs has generally found strong numbers for Warren and more negative ones for Biden than many pollsters, so once model adjusts for house effects, this poll counts as just 16 percent for Warren and 18 percent for Biden (Sanders’s figure, on the other hand, didn’t really shift).
  • Meanwhile, David Binder Research’s final poll on behalf of Focus on Rural America found Buttigieg leading Sanders by 2 points, 19 percent to 17 percent, with Biden and Warren tied at 15 percent and Klobuchar at 11 percent. While it’s somewhat surprising Buttigieg was in the lead, as he hasn’t led in other recent polls, our model basically had Buttigieg and Sanders tied at 19 percent instead once we adjusted for house effects, as this pollster has tended to give Sanders lower marks than other pollsters.
  • Data for Progress also conducted its own survey and found Sanders in first with 22 percent. But the field as a whole was very clustered, with Warren just behind at 19 percent while Biden and Buttigieg each had 18 percent. But because Data for Progress’s polls have been friendlier to Warren and Buttigieg, the model discounted each of their percentages by about 2 points.
  • Lastly, Emerson College’s final survey of Iowa found Sanders in the lead with 28 percent, with Biden 7 points behind at 21 percent. Buttigieg and Warren were at 15 and 14 percent, respectively, while Klobuchar was at 11 percent. But this poll wasn’t actually as good as it sounds for Sanders, as Emerson has consistently found very good results for him. After accounting for house effects, his percentage was closer to 22 percent in our model.

Overall, these last few surveys were fairly good for Sanders, but remember that on average, the polls show a pretty wide-open race. And there could be a polling surprise flying under the radar, as only two of these new polls included survey interviews from this weekend. Moreover, because of the rules Iowa Democrats use in their caucuses, there are many moving parts that add to the uncertainty — voters’ second choices and the realignment process where voters can switch their preferences could come into play. We’ll be tracking all that and more in real-time on our live blog, so be sure to join us as we watch the results come in tonight, starting at 7 p.m. ET!

Geoffrey Skelley is an elections analyst at FiveThirtyEight.

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