Super Tuesday: 4 Candidates, 4 Storylines

It's here at last: Super Tuesday, the day 10 states cast their ballots in the 2012 primary. Here's what's at stake for each of the candidates today:

• Mitt Romney—Expected to win: Massachusetts, Vermont, Virginia. Really wants to win: Ohio and Tennessee. Winning both would give him both of America's top swing states (Ohio and Florida), and a win in the South, and make him, in the Wall Street Journal's words, "the presumptive leader." Keeping an eye on: Romney's camp says it's shifting into delegate-acquisition mode, so though it won't win Georgia and it's not expecting Tennessee, it's invested in the Atlanta and Knoxville regions.

• Rick Santorum—Expected to win: Oklahoma. Has a shot in: Ohio, even though the AP says he has a "shell of a campaign" there. He's also a slight favorite in Tennessee. Keep an eye on: The Catholic vote, which Santorum has so far failed to win in any state, despite frequently discussing his Catholic upbringing. It'll be a good test to see if his JFK vomit tirade hurt him long-term.
• Newt Gingrich—Expected to win: Georgia. Playing for: Second place anywhere else. His best shots are in Oklahoma and Tennessee, and Politico thinks falling to third in either would amount to a "rough night for Gingrich, although he's soldiering on regardless."
• Ron Paul—Expected to win: Something, hopefully. Really wants to win: Anywhere at all. With no wins yet, and an increasing reputation as a Romney surrogate, Paul needs a W to stay relevant. He has a shot in today's caucus states, particularly Alaska and North Dakota.