I'm watching Russert's cable show on MSNBC right now--he's got the ever-wise Chuck Todd on, along with Andrea Mitchell and David Gregory. (By the way, I feel like we at TNR are always saying how much better MSNBC's coverage is than its cable rivals'. I didn't catch too much of it Thursday night, but that rule seemed to apply based on what I saw...)

Anyway, Todd was making what I thought was a pretty provocative point, though maybe I've been away from the DC pack too long to know what the current mood is. (Got out of Iowa late yesterday, then laid low when I got here. Back into the bubble for tonight's debates...) Todd was arguing that New Hampshire is actually a must-win for Obama. If he loses, it'll be a huge let-down after all the Iowa momentum. Meanwhile, Hillary notches a stunning come-from-behind victory--the "other comeback kid" narrative will be irresistible--and there's a long time for that narrative to harden before South Carolina. The only contest along the way is Nevada, which is a caucus state and which Harry Reid's machine might well deliver for her. (Reid hasn't endorsed her but his son has.) And if that momentum vaults her to a win in South Carolina, it's hard to see how she stumbles on February 5...

As I say, it's a provocative theory--well worth chewing over. But I think the flaw is South Carolina, which kind of gets glossed over here. Now that Obama has demonstrated he can win in overwhelmingly white areas, black voters are much more likely to support him there, even if he stumbles in New Hampshire. Also, I think the length of time between New Hampshire and South Carolina actually helps Obama if he loses here. It gives him time to go back to work all over again, just like he did in Iowa. Anyway, you can't simultaneously argue that the closeness of two primaries (Iowa and New Hampshire) magnifies the importance of momentum, and that the distance between two others (New Hampshire and South Carolina) does the same thing.

That's not to say South Carolina's a lock for Obama regardless of what happens here. Far from it. Just that South Carolina stays winnable for him under most of the scenarios I can imagine.

So I guess my bottom line is: New Hampshire is a must-win for Hillary. If she pulls it off, then South Carolina is a must-win for Obama. And, if he pulls it off, then welcome to the Risk-board-on-steroids that is February 5.

--Noam Scheiber