Slate's John Dickerson:

... According to entrance polls, of those voters who wanted a true conservative, Santorum got 36 percent and Romney got just 1 percent. (That is not a misprint.)

Though the top two candidates tied, Santorum was the big winner. Weeks ago, the smart people thought that tonight he'd be addressing an empty ballroom of lonely, sad balloons. Instead, the crowd at his victory party is so thick I've practically got supporters on my lap as I type this. Santorum is now the only Flavor of the Week candidate to actually win anything, which makes him a genuine threat to Romney, at least for the moment.

... One of the open questions going into the caucus was how much evangelical voters would participate. They turned out in the identical numbers as the last caucus, with 58 percent of the voters self-identifying as evangelical. They helped Santorum with his surge. "Everyone talks about the economy," said Bill Yewell of Augden, "but Santorum comes at it from a different way. If we take care of the social issues and the family, the economy will come around."