Noam, on the Democratic side, there are different schools of thought about how second-choice votes might work. As you hinted, I'll have more on this in a longer piece shortly. But two points to add. One is that Obama supporters say they don't expect to see Hillary pick up many second-choicers. The rationale is that Hillary was the default choice in the race--being for or against her was the starting point for any voter's decision--and if someone hasn't backed her by now, they're not likely to come around. (Not sure that I buy that, personally.)
The other point is that, within the campaigns, there's some division about how much this is going to matter. Some people say it could be decisive, but others think that Biden and Richardson and fizzling out fast, with Dodd a non-entity, and there's just not many non-Hillary/Obama/Edwards people remaining out there.
A related thing to keep an eye on is the emerging struggle between Biden and Richardson for fourth place. One of those guys just might be able to carry on into New Hampshire, especially if one should outperform expectations and John Edwards should underperform. That could set up a narrative of Hillary versus Obama with a sleeper on the margins. Not that I would want to be that sleeper....
--Michael Crowley