538 - Buttigieg And/Or Sanders Are Going To Win Iowa. What Happens Next?

Pete Buttigieg and Bernie Sanders each led at least one of the three metrics that Iowa Democrats finally released on Tuesday, reflecting the various ways that Iowa counts its caucus votes. State delegate equivalents, the measure that has gotten by far the most attention from the media because it’s traditionally the way that Iowa has counted its vote, showed Buttigieg ahead 27 to 25 percent, with 62 percent of precincts reporting. But Sanders narrowly led in two measures of the popular vote, taken before and after voters were given the opportunity to realign to a new candidate if their original choice was deemed not viable.

If the split verdict holds, it will be an appropriately weird outcome for a weird-as-hell Iowa caucus. But it also comes at a rather awkward time for our forecast model, which tries to anticipate how polls could change after Iowa. The weirdness makes it harder to guess which direction polls will change in and by how much. (For the time being, the model is still frozen until we get more complete Iowa results.)

The basic way the model works once a state finishes voting is this: It makes educated guesses about how each candidate’s standing in national polls and in subsequent states will improve or decline based on how well they did, accounting for both their share of the vote and whether or not they won the state. This performance is then measured relative to “expectations,” which the model defines as national polls, adjusted by regional factors. The fact that Buttigieg did much better in Iowa (27 percent of state delegate equivalents so far) than his national polls might imply (he’s at only 7 percent nationally) would suggest the possibility of a fairly large bounce, for instance — although the model slightly discounts Buttigieg’s performance since Iowa is a Midwestern state and Buttigieg is from the Midwest.

Our research also finds that much (though not all) of the bounce after major states vote is binary, meaning that who wins the state matters a lot. It isn’t necessarily a continuum. So when there are multiple potential definitions of the winner, that creates a problem.

https://fivethirtyeight.com/features/buttigieg-and-or-sanders-are-going-to-win-iowa-what-happens-next/