U.S. Republican presidential hopefuls Mitt Romney and Rick Santorum are campaigning Monday in Michigan, where the two are in a tight race on the eve of a nominating contest there.

Michigan and the southwestern state of Arizona hold Republican primaries Tuesday, a week before the much-anticipated “Super Tuesday,” when 10 states hold presidential nominating contests. Republicans are selecting a candidate to face Democrat Barack Obama in the November presidential election.

Opinion surveys from Arizona show Romney, a former Massachusetts governor, with a clear lead over Santorum, who was a U.S. senator from Pennsylvania.

Although Michigan is the state where Romney was born, he is having difficulty winning the support of social conservative voters who are rallying behind Santorum. Polls from Michigan show the men in a virtual tie, while Texas Representative Ron Paul and former House speaker Newt Gingrich trail.

Paul is campaigning in Michigan Monday, while Gingrich is focusing on the state of Tennessee, before beginning a tour Tuesday of Georgia, the southeastern state he represented in Congress.