Factbox: Wisconsin Republican primary vote

April 3 - The race to win the Republican Party's nomination to oppose President Barack Obama in the November general election turns to the Midwestern state of Wisconsin on Tuesday.

Here are a few facts about Wisconsin and the primary.

Forty-two delegates are up for grabs in Wisconsin's winner-take-all contest where 18 delegates will be awarded on a state-wide basis and another 24 per congressional district. The primary is open, meaning registered Democrats and independents can vote in the Republican contest.

Wisconsin's estimated population for 2011 was about 5.7 million, according to the U.S. Census. Unemployment in February was 6.9 percent, according to the U.S. Bureau of Labor Statistics. Election officials project that up to 35 percent, or about 1.5 million, of the state's voters will take part in the primary.

Wisconsin Governor Scott Walker faces a recall election on June 5, becoming the first U.S. governor to face a no-confidence vote in nearly a decade. A Republican, in 2010 Walker pushed through legislation stripping public-sector unions of most of their bargaining rights. Walker has not endorsed any of the candidates.

Polls show Mitt Romney, a former governor of Massachusetts, leading Rick Santorum, a former senator for Pennsylvania. Romney already has a large lead over Santorum in the race to amass the 1,144 delegates needed to win the Republican presidential nomination.

The state's Republican base is less religious than many. This could hurt Santorum, who has relied on the backing of evangelical Christians in other contests. In the state's 2008 Republican primary, 62 percent did not identify as born-again or evangelical Christians, exit polls show.

(Reporting By Lily Kuo; Editing by David Brunnstrom)