Florida primary day. I wrote something over at Plum Line arguing that it matters whether Romney wins by a narrow margin or by a landslide because it will influence how he behaves over the next five weeks, through Super Tuesday.
The other question, I suppose, is whether this is the end of the line for Rick Santorum. I think so, although as usual I'll remind everyone not to trust immediate candidate reactions. After South Carolina, I thought that it made sense for Santorum to stay in for a week because of the possibility of a third-candidate effect: I thought that it was possible that with Mitt and Newt attacking each other full force, it was possible that Santorum might benefit even if he didn't have the money to run much of a campaign of his own. It appears that it didn't pan out, and I can't see any point in Santorum continuing on.
So why did Santorum fizzle after Iowa? That he did well there was, I still think, somewhat of a low-probability fluke. But once he emerged as a potentially viable conservative opponent to Romney, why didn't he do better? I guess I have four theories I can think of. One is that Iowa is no longer very important. Or, more likely: that Iowa has produced a sufficiently long string of social conservative surprises (Pat Robertson, Mike Huckabee) that the press heavily discounts any social conservative who does well there. That's silly; Iowa is not, in fact, a social conservative outlier within the GOP. But it might be true anyway. The second theory is a press bias in favor of Newt Gingrich. He's easy to write about, and many members of the elite press have always been easy marks for the snake oil that he peddles. So instead of writing him off after his lousy finishes in Iowa and New Hampshire, the press continued to treat him as a top-tier candidate, thus taking time away from Santorum. So I have two press-centric theories, and I'll add one voter theory: Santorum doesn't seem to do resentment particularly well; the best he can manage is a sort of whine, such as when he wasn't being called on enough in early debates.
And then there's theory four, which is party-based. It appeared, through Iowa, that party actors were willing to accept Romney but were not sold, which meant there was room for a non-Romney to emerge. It's certainly possible, however, that either party actors don't much like Santorum for whatever reason -- or, more likely, that they really were a lot happier with the Mittster than they let on. If that's the case, the nomination was probably a done deal well before Iowa, even though on the surface (compared to, say, 2000 in both parties) there seemed to be reason for uncertainty.
I have no idea which, if any, of those theories explains it, but I do think it needs a bit of explaining.