More so than Arizona, Michigan is where the high stakes primary will be taking place. Mitt Romney and Rick Santorum are in a statistical tie for first place in a state Romney had once expected to easily win.
"It's good to be in Michigan, a lot of stories here, deep roots here," said Romney
A victory in Michigan- the state where he was born and where his father served as governor- could cement Romney's status as presumptive nominee. But a loss to Santorum could deal a major blow to his campaign.
"We want to make sure we get Republicans out to vote," said Romney at his campaign headquarters in Michigan on Tuesday. "We want this to be a process where Republicans choose the Republican nominee, we don't want the Democrats to choose who they think is easiest person to run against."
Romney was referring to a little controversy stirred up by Santorum Monday night. Because voters can switch their party affiliation last-minute, he confirmed his campaign was making robo-calls to Democrats to get them to vote against Romney.
"One of the things that Governor Romney and his people say is 'well he can't attract Democrats,' well guess what we'll wait and see," said Santorum.
"It's confusing to people, it's a new low in this campaign," said Romney.
The former Massachusetts governor has been touting his business background in the state, which was hit hard by the recession.
"I understand why jobs go, why they come," said Romney. "Senator Santorum's a nice guy, but he's never had a job in the private sector."
Santorum, a former Pennsylvania senator, has been playing up his conservative credentials.
"I believe in markets, I believe in free people," said Santorum. "I don't believe in government telling people what to do. We need someone like that running against Barack Obama, not someone who did 'Obamacare light.'"
Both candidates have kept their focus on Michigan since last week, as Romney now appears to have a solid lead in Arizona.
Newt Gingrich effectively skipped both states, and is counting on a strong performance in the south on Super Tuesday, which is in one week.
Ron Paul briefly campaigned in Michigan, and is working toward amassing enough delegates to have some sway at the Republican National Convention in August.
Santorum will campaign Tuesday around Grand Rapids, a city home to many social conservatives and tea party supporters. Romney is set to meet with voters in suburban Detroit, an area with a larger collection of moderate Republicans, a key segment of his support.
No matter the top finisher, Romney and Santorum stand to split the 30 delegates at stake because Michigan distributes delegates proportionally. By contrast, Romney is favored to capture all 29 delegates in Arizona, which features a winner-take-all system.
Romney has 123 delegates to 72 for Santorum, 32 for Gingrich and 19 for Paul in the Associated Press count, with 1,144 required to win the party nomination.