U.S. Republican presidential hopefuls Mitt Romney and Rick Santorum are competing in two closely watched state primaries Tuesday after a day of campaigning in one of them — 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 he touted his own ability to create jobs.

“I happen to believe that if we want to have a strong economy and good private sector jobs, it helps to have a president who's had a private sector job and I have.”

Santorum told supporters in Michigan that his campaign did not expect to be doing so well in the state. He said this fact shows the potential his campaign has. He said his plan for improving the economy includes reducing the size of government.

“We will hit the ground running on lowering the budget. Every year we will spend less money in Washington than we did the year before. That's the budget I will propose. We will shrink the size of government.”

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.