The most striking stat IMHO from CNN’s exit poll of the Michigan primary.
Santorum overperformed among voters who strongly support and strongly oppose the Tea Party. The former is evidence for what smart people have been saying forever: the idea that the Tea Party is some kind of libertarian vanguard rather than a synonym for “partisan Republican activist” is a joke.
The latter is evidence that 1) Operation Hilarity was somewhat successful, 2) some blue-collar Democrats genuinely like Santorum for his affect (many Democrats who voted for Santorum had a favorable view of him, so it wasn’t all tactical voting). Which means that tribalism and cultural affectations are a big deal, since Santorum’s economic policies are, if anything, more regressive than Romney’s.