Nate Silver: Who’s Winning Iowa And New Hampshire?
Nate silver's two different results as measured by two different methods.
http://fivethirtyeight.com/features/whos-winning-iowa-and-new-hampshire/
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The first model, which we call polls-only, is based only on polls from one particular state. (Iowa polls in the case of Iowa, for example.) It’s basically an updated version of the model we used for the primaries four years ago.
The second model, polls-plus, also considers endorsements and national polls, in addition to state polls, and tries to consider the effect that Iowa and New Hampshire could have on subsequent state contests. (National polls aren’t necessarily a positive for a candidate in the polls-plus model; instead, it’s a bearish indicator when a candidate’s state polls trail his national numbers.)
Historically, polls-plus would have been somewhat more accurate, but it’s pretty close — so we think the models are most useful when looked at together. Indeed, they present different perspectives on the races this year, mostly because of that endorsements variable, which helps Hillary Clinton and Marco Rubio but hurts Bernie Sanders and Donald Trump. If you take a strictly empirical view of the primaries, accounting for the establishment’s historical tendency to win out in the end, you’ll probably prefer the polls-plus model. If you think “this time is different” — or you’re a Trump or a Bernie fan — you’ll probably like polls-only instead.
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Iowa: Because public opinion can shift rapidly in the primaries, our models put a lot of emphasis on the most recent polls. That’s good news for Sanders, who has been neck and neck with Clinton in Iowa polls published this month after trailing her for most of last year. In fact, the race is nearly a tossup: He now has a 45 percent chance of winning Iowa according to polls-only, although the polls-plus model, noting Clinton’s dominance in endorsements, is more skeptical of Sanders, giving him a 27 percent chance instead.
New Hampshire: Here, there’s a split between the models. Sanders is a 73 percent favorite according to polls-only, while polls-plus — noting Clinton’s advantage in endorsements and that she’s favored in Iowa — gives Clinton the slightest edge, with a 53 percent chance to Sanders’s 47 percent. Essentially, she’d be following the path that Al Gore took over Bill Bradley in 2000, when an Iowa victory propelled him to a narrow victory in the Granite State. But the polls-plus model is designed to lower the effect of the endorsements variable to zero by election day in each state. So if Clinton keeps falling in New Hampshire and Iowa polls instead of rising, the establishment may not be able to bail her out, and she’ll have to contemplate the possibility of being swept in both states.
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