Type of election: Primary
How it works: 42 delegates are at stake, 18 awarded winner-take-all at the statewide level, the rest awarded winner-take-all by congressional district. The primary is open.
Official election results: Wisconsin Government Accountability Board
Republican candidates: Newt Gingrich, Ron Paul, Mitt Romney and Rick Santorum (all others have dropped out or are polling at less than 1 percent)
Democratic candidates: There is no competitive Democratic primary.
Previous performance: In 2008, Romney withdrew before the primary. Paul finished third with just over 4.5 percent of the vote. Obama won the Democratic primary with 58 percent of the vote.
Television stations: Full list
Latest polling: New York Times:
Nate Silver gives Romney a 91 percent chance of winning the state and Santorum 9 percent.
Bottom line: Santorum's best chance to make some news today is to pull something off in Wisconsin, but the chances don't look good. It is an open primary, though, and Wisconsin voters are at a heightened state of alert because of the recall elections, so some crossover vote could allow Santorum to overperform.