No one, not even the candidates, anticipated the slugfest that is shaping up in Michigan as Rick Santorum and Mitt Romney head toward the final hours before Tuesday's Republican presidential primary vote.

But anyone watching the ad campaigns in Michigan this week has a clue how close this race has become.

The stakes are very high, particularly for Romney. A failure to achieve anything other than the top spot in the state where his dad was governor for three terms could prove to be a dramatic momentum killer -- enabling Santorum to bolster his argument that Romney is far from the presumptive GOP nominee.

Making the rounds in the Wolverine State, Santorum said he didn't expect to be competing at this level, but he is very excited.

"You here, in Michigan, everyone thought: 'Oh, this is going to be a sleepy little primary.' You know we have one of the candidates who claims a lineage here in the state of Michigan, although I do believe he was governor of Massachusetts, not Michigan," Santorum told an audience on Monday.

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Romney has at least once framed himself as the underdog in his home state.

"I think I can show that I can fight real hard and come from behind and I think the people as they're focused on my campaign and my candidacy and my plan to get people working again,” he said.

The latest Mitchell-Rosetta Stone poll out Monday showed Santorum had pulled into the lead, 37 percent to Romney's 35 percent. Newt Gingrich, who hasn't campaigned in Michigan was pulling 9 percent, neck-and-neck with Ron Paul at 8 percent.

But the latest Real Clear Politics average gives the top spot to Romney with 37.3 percent of recent polling. Santorum is following within the margin of error at 35.8 percent of Republican voters polled.

The beneficiaries of the slugfest are Michigan television and radio stations, which are bombarding Michigan voters with political ads paid for by the campaigns and their surrogates.

"I just tune them out now," said Michigan Republican voter Norma Frane. "I go and get my coffee. I don't listen to the details because it is just overwhelming."

The conventional wisdom is that voters hate negative political ads but remember their content. However, a panel assembled by Fox News at a hotel in Troy, Mich., bucked that trend.

Of all the ads the panelists said they have watched, the one that stuck out in their minds was one in which Romney was selling himself as the hometown hero.

"Really, the most effective ad I've seen is the one with Romney where they show him with his Michigan roots in his truck," said panelist Lorie Steinhauer. Her thoughts were quickly echoed by recreational fisherman and newcomer to politics John Piotrowski.

"People in Michigan, we're going to go, 'yeah, I can relate to that,'" Piotrowski said.

Michiganders quickly became wise to the practice of allowing super PACs -- the unregulated, uncoordinated groups that support or oppose candidates -- to handle the dirty work on the airwaves.

"When you see an ad sponsored by a candidate ... it's showing what a great guy he is. It's those other groups that aren't affiliated that are throwing those other attack ads out there," Piotrowski said.

Because of that, the panelists said they were not swayed by tendentious ad campaigns.

"All they do is they make me go do research. I will then go see if it is true," said Jennifer Hensley. "They use one sound bite and it is always, always out of context."

The panelists also said the GOP will not be hurt by the bitter sparring matches in the primary because the party will unify for the general election.

With Paul and Gingrich far behind, Michigan voters are looking at this primary as a two-person contest.

"Nobody really pays attention to Gingrich or Paul. They're out there. But the main stories everywhere are Romney and Santorum," Piotrowski said.

However, Michiganders have not concluded that Gingrich is singing his swan song.

"In any other year, I'd count him out," Hensley said. But not this year in which the primary contest so closely resembles a game of king of the hill.

"I wouldn't write him off 'cause he knows what he is doing and he could become a factor again. He could end up becoming No. 1," said Armand Coallier.