(Reuters) - The race to win the Republican Party's presidential nomination to challenge President Barack Obama reaches a new pitch on "Super Tuesday" when 10 U.S. states, including Ohio, hold primaries and caucuses.
Here are some facts about the Ohio Republican primary.
* The politically divided Midwestern state is the most important of the Super Tuesday contests. Ohio will send 66 Republican delegates to the Republican National Convention in August, second only to Georgia of states voting on Tuesday. In a battleground state in the general election, the primary could indicate how the eventual Republican nominee will perform there in November.
* The primary comes down to a dual between Rick Santorum, a former senator for Pennsylvania, and Mitt Romney, former governor of Massachusetts and the front-runner in the overall Republican race. Ohio is seen as a must-win for Santorum. The two have been in a statistical dead heat over the last few days.
* With a population estimated at 11.5 million in 2011, Ohio was the seventh most populous U.S. state.
* Ohio's unemployment rate, which was 7.9 percent in December 2011, was slightly under the national average of 8.5 percent for the same month, according to the U.S. Bureau of Labor Statistics.
* In 2010, Caucasians made up about 83 percent of the state, African Americans comprised 12 percent and Hispanics about 3 percent of the population, according to the U.S. Census.
* Historically, Ohio has been a strong union state. Although union membership is in decline, the 13.4 percent of workers who were members of unions in 2011 is still higher than the national average of 11.8 percent, according to the Bureau of Labor Statistics.
* Ohio is a so-called swing state but leans Republican. No Republican has ever been elected president without winning Ohio.
(Reporting By Lily Kuo; Editing by Deborah Charles)