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So what can we say about the race? First is that it's very close. The final PollTracker average shows Clinton 47.9% and Sanders 44.6% - a three point race. The Selzer poll - the Iowa gold standard - also has it as a three point race - albeit at Clinton 45% and Sanders 42%. The last seven polls are all in Clinton's favor with the exception of a poll today from Quinnipiac which has it by three in Sanders' favor. So close but with a slight edge by Clinton basically any way you slice it. (One of the two polls released today shows Clinton with an 8 point lead. But it's a lesser known pollster and it appears to be an outlier. Unless it's not.)
If you look at the numbers in the chart you can see that Sanders pulled basically even mid-month. But Clinton has stabilized her slim lead since then.
I would say that for a Caucus, where turnout is harder to measure than in primaries, and where the threshold could potentially toss the handful of O'Malley supporters decisively in one direction or another, the race is simply too close to call, though a very mild move in Clinton's direction does seem perceptible.
So what to look for? See who wins.