Who's going to win tonight in Iowa? No one knows. Certainly including me. But I do have a bit of value added here, although only after a couple of paragraphs of digressions & links.
Allow me first a bit of self-indulgence (or skip down to the next paragraph), but, well, here's what happened. I was included (thanks to my posting over at Greg Sargent's Plum Line) in a WaPo list of pundit predictions about the Iowa results. And while I try hard not to complain about editing, I'm slightly miffed about this one. They took out the first words of my explanation for my selection of Rick Santorum, which were "I really have no idea who is going to win." Ah well; next time, I'll emulate Dana Milbank, who wisely and safely predicted a Gary Johnson victory -- after a late-afternoon Huntsman surge fizzles out.
Anyway, for analysis of the polls, I'll direct you to Mark Blumenthal, who thinks that Romney will probably win, and Nate Silver, who also has Romney as the most likely winner but puts more stress on uncertainty. Those are both "polls of polls" types of analysis. Want to go to the next level? Harry Enten takes the next step, and does a poll of "polls of polls"; that is, he looks at all the models or averaging methods out there. His numbers come up Romney, too (yes, yes: by 2020 there will probably be a dozen or more Nate Silvers, and a handful of Entens, and therefore there will be a market opening some current sixth-grader will fill for someone to average the polls of polls of polls. That's the kind of US ingenuity that won the Cold War, folks).
I think it's time for that value added I promised up top. Here's the thing: all of the quantitative stuff found in the links in the previous paragraph are averages or models based only on what's in the top-line numbers available in the various polls out there. But we know of other factors that may cause candidates to over- or under-perform their poll numbers. So I figured it's worth it to go through all of them I can think of and note how they (may) affect each candidate. Note that if we actually knew how this stuff would work, we could incorporate it into the polling; the problem whether any of these effects will matter at all is unknown. Ready?
Organization: campaigns identify supporters and do whatever they can to get them to their caucuses. That's normal; what's different in caucuses is that each GOP meeting will feature speakers on behalf of each candidate -- if, that is, the campaigns have found someone to do it in that precinct. Helps: Romney, Paul, and Perry are said to have the most precincts organized. Hurts: Gingrich is almost certainly the least organized of the six
Strategic Voting: If you're a social conservative and don't trust Mitt Romney on the issues you care about, you may be relatively indifferent about several possible anti-Romneys, and shift your vote to whoever is doing best. Other shifts for other groups are possible, too. Helps: Santorum, perhaps Romney. Hurts: Gingrich, Bachmann, possibly Perry.
Iowa Conservative Turnout Bias: Nate Silver talked about this one. Candidates perceived as conservative tend to overachieve compared to polling in Iowa; moderates tend to underachieve. Helps: Santorum, Perry, Bachmann, and perhaps Gingrich. Hurts: Romney.
Enthusiasm: An obvious one; candidates with enthusiastic supporters should tend to overperform. Helps: Paul, of course. Hurts: harder to tell, but probably everyone else.
Momentum: Let's define this (as Silver's model does), for the purpose of this exercise, as simply extending recent trends to account for the time between the last polls and actual voting. In other words, if people were moving towards a candidate over the weekend, it makes sense that whatever was causing that would probably still be operating yesterday and today. Note that this one overlaps with some of the others, especially strategic voting, but it isn't quite the same thing. Helps: Santorum. Hurts: Paul, Bachmann. Gingrich was losing supporters until recently, but he's been pretty flat over the last week.
Late Campaigning: This one should almost completely overlap the previous one, but it's worth noting that some candidates were probably throwing a lot more money at TV screens across Iowa over the last few days than others. Helps: Perry, Paul, Romney. Hurts: Gingrich, Santorum, Bachmann.
Regional Weather Effects: Caucus attendance is presumably more sensitive to bad weather than primary voting would be, and to the extent that neither weather nor candidate support is uniform across the state, it's easy to imagine fairly significant effects here. Helps and hurts? No idea. Ask reporters for this one.
Am I missing anything? Important caveats: in addition to what I said above about not knowing the magnitudes of any of these, or even whether they exist, my "helps" and "hurts" categories are just my speculative impressions of what's going on there. It's certainly possible, and perhaps likely, that anyone who has dug more deeply into the polls and the detailed campaign reporting might have a convincing argument for why I got one of these wrong.
My general sense of this -- and again, it's just guesswork at this point -- is that Santorum was on the good side of a lot of these effects, and Gingrich was on the bad side. But what that means for tonight...we're just guessing.