(Reuters) - The race to win the Republican Party's presidential nomination to challenge President Barack Obama reaches a new intensity on "Super Tuesday" when 10 U.S. states, including Oklahoma, hold primaries and caucuses.
Here are some facts about the Oklahoma Republican primary:
* Polls show former U.S. Senator Rick Santorum of Pennsylvania, a social conservative, ahead of former Massachusetts Governor Mitt Romney, the overall front-runner. The state will award 43 delegates, mostly through a proportional formula.
* Oklahoma is socially conservative with a large population of evangelical Christians. In the 2008 general election John McCain won all 77 of the state's counties and 66 percent of the vote compared to Obama's 34 percent - the highest Republican percentage of any state. In the 2008 Republican primary, Romney won 25 percent of the vote to McCain's 37 percent.
* Unemployment was 6.3 percent in December 2011, data from the U.S. Bureau of Labor Statistics showed, below the national average of 8.5 percent for that month, but poverty is still a problem in the state. About 16 percent of Oklahomans live below the poverty level compared with the national average of 13.8 percent.
* Voter turnout in the 2008 Republican primary at 335,054 set a new record for the state.
* Oklahoma is a major producer of natural gas. The state utilizes a much scrutinized extraction technique called "fracking," that unlocks gas trapped in shale rock through hydraulic fracturing. Critics say the method harms local water supplies and could cause seismic tremors.
* Oklahoma has not voted for a Democrat for president since 1964.
* Oklahoma U.S. Senator Tom Coburn endorsed Romney in an editorial in The Oklahoman, the state's largest newspaper. State legislators have spread their support between Romney, Santorum and former U.S. House Speaker Newt Gingrich. Mary Fallin, the state's first female governor, has not made an endorsement.
(Reporting By Lily Kuo; editing by Ros Krasny and Eric Beech)