GOP ad wars heat up in Michigan ahead of pivotal primary Mitt Romney speaks at a town hall meeting at Eagle Manufacturing Corporation in Shelby Township, Mich., Tuesday, Mich., Feb. 21, 2012. ROSEVILLE, MI -- Bringing the state's emerging status as a crucial contest for the Republican presidential race into stark relief, the campaigns of Mitt Romney and Rick Santorum bombarded Michigan with new ads on Thursday -- and President Barack Obama's campaign got in on the act, too. Television and radio ads are blanketing the Great Lakes State ahead of its pivotal Tuesday primary, which has been transformed into a proxy battle for momentum in the race for the GOP nomination. Santorum's campaign announced a new TV ad, "Say What," which seizes on past comments by Romney that frame the former Massachusetts governor as a liberal, or at least a conservative of convenience. It's just part of an effort by Santorum to parry the millions spent by Romney and a supportive super PAC to avoid an embarrassing defeat in a state where Romney was raised, and his father served as governor. Michigan radio listeners on Thursday might have heard, for instance, advertisements featuring audio of Santorum defending earmarks -- a congressional privilege which conservatives find distasteful -- and Romney boasting of his desire to cut spending. The Santorum campaign's "Say What" ad. The offensive is part of an all-out effort by Romney to ensure victory here, an outcome which an adviser to Romney's campaign guaranteed Wednesday evening following a debate in Arizona. "We're going to win Michigan," strategist Stuart Stevens told reporters following the debate. To that end, Romney returns here on Thursday evening, where he'll rally with Tea Party voters. He's set to deliver a major economic speech Friday morning at Ford Field, the home of the Detroit Lions. But a minor snowstorm forecast for overnight could put a damper on the enthusiastic crowds here. "What I'm hearing right now is that it's pretty close to the national polls," said Republican State Sen. Ken Goike, who represents a district in the center of Macomb County. I think Santorum is leading in my district, but not by much. If the national polls are tight, so are the ones in Michigan. An NBC News/Marist poll released Wednesday morning found Romney leading Santorum, 37 percent to 35 percent. A Detroit Free Press/WXYZ poll released that evening pegged Santorum as the campaign's leader, 37 percent to 34 percent. The Romney campaign might be buoyed by a new endorsement Thursday morning from the Detroit Free Press, which accompanies similar backing from the city's other major paper, The Detroit News. Santorum's debate performance in Arizona has also faced criticism for mangled answers that highlighted Romney's criticism of Santorum's career in Washington. But apparently discontent to allow the fight in Michigan play out on its own, Obama's campaign weighed in with a new television ad that was a thinly-veiled effort to highlight Romney's opposition to the 2009 auto bailouts. The ad specifically cites Romney's 2008 op-ed advocating bankruptcy for General Motors and Chrysler, contrasting it with Obama's decision to provide support to the troubled automaker -- a popular decision, even with Republicans, here in Michigan, where the auto industry looms large. The campaign spent about $43,000 on the spot. Priorities USA, the super PAC backed by Obama, also got in on the advertising action. That group's ad more explicitly targets Romney over the auto bailouts in an effort to hurt the former Massachusetts governor, and, at the very least, extend and bloody the GOP primary. Priorities USA put about $230,000 behind its ad.