The battle for Michigan is officially on.

Eight Republican candidates may be rolling into metro Detroit for tonight’s presidential debate at Oakland University, but the Democratic National Committee picked one – Mitt Romney – to target in full-page advertisements in today’s Free Press and Detroit News.

The headline? “What was Mitt Romney’s plan for Michigan’s automobile industry? ‘Let Detroit go bankrupt.’”

President Barack Obama’s campaign and his Democratic allies have been hammering away at the point that Romney wrote an op-ed column in the New York Times in late 2008 opposing any taxpayer funds being used to help out General Motors and Chrysler.

Romney’s line of explanation to date has been that, in the end, the Obama administration did exactly what he had called for: run the companies through a structured bankruptcy that forced them to shed debts – and shareholders to take a loss – while saving the companies.

The back-and-forth though underscores how important Michigan may be in next year’s election, particularly if Romney, who was born and grew up here and whose father was a popular three-term governor, wins the Republican nomination.

Romney opined Tuesday on CNBC – the host of tonight’s debate – that Obama policies have “failed Michigan,” a pretty bold rejoinder given the automakers’ turnaround since the rescue in late 2008 and early 2009.

But as Romney said in his piece, unemployment in Michigan remains over 11% and in Detroit, “the city of my birth, far higher joblessness has brought a great city to the edge of ruin.”

“There will be no one on that stage this week more pained by Michigan’s struggles than I am,” he said. “If we want to create jobs in this country once again, there’s a better path.” Romney has called for cutting taxes and regulations and repealing the Democrats’ health care reform legislation – even as Democrats have credited Romney’s model enacted when he was governor as Massachusetts as a model for it.

One group, calling itself “Protect Your Care,” plans to stand outside the debate tonight and collect thank you notes and cards “thanking Romney for his role in the design” of the health care reform bill. Romney has repeatedly defended the plan in Massachusetts, which shares similarities with the national bill, but has also said repeatedly that he does not think it is the right model for the nation and should be repealed.

Tonight’s debate is attracting a lot of attention, as Romney’s chief rival for the nomination at this point – former Godfather’s Pizza CEO Herman Cain – battles back against accusations of sexually harassing women years ago. Cain has steadfastly denied the accusations.

Several groups are expected to protest Republican policies outside the debate hall in Rochester tonight, UAW members among them.

The debate begins at 8 p.m. and is scheduled to last for two hours.