U.S. Republican presidential hopefuls Mitt Romney and Rick Santorum are competing in two closely watched primaries after a day of campaigning in Michigan.

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 Democratic President Barack Obama in the November 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.

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

On Monday, Romney criticized Santorum on the campaign trail, saying the former senator is not spending enough time talking about the economy. Romney said Santorum has never had a job in the private sector and touted his own ability to create jobs.

Santorum told supporters in Michigan that his campaign did not expect to be doing so well in the state and said this fact shows the potential the campaign has.

Paul also campaigned in Michigan Monday, while Gingrich focused on the state of Tennessee, before beginning a tour Tuesday of Georgia, the southeastern state he represented in Congress.