Mitt Romney's campaign is up with its first ad in Michigan, using it to tout his ties Detroit.

The decision to go on the air indicates the campaign is concerned about Rick Santorum, who led in two polls of the state released on Monday. Michigan is considered a must-win for the Romney campaign.

Santorum has said he and his campaign will "plant our flag" in Michigan and compete hard for delegates there. The former Pennsylvania senator is scheduled to be in the state on Thursday.

Romney's ad highlights his childhood in Michigan, where his father served as chairman of American Motors and later as governor.

"When I grew up in Michigan it was exciting to be here. I remember going to the Detroit auto show with my dad. That was a big deal," Romney says in the ad as images of Detroit in the 1960s and pictures of him as a young man in Michigan are juxtaposed with video of the city today. "How in the world did an industry and its leaders and its unions get in such a fix that they lost jobs, that they lost their future? President Obama did all these things the liberals have wanted to do for years, and the fact that you've got millions of Americans out of work, home values collapsing — people here in Detroit are distressed."

Romney then stresses what the city and state mean to him. "I want to make Michigan stronger and better," he says. "Michigan's been my home, and this is personal."

A super-PAC supporting Romney has been on the air in the state for more than a week, but this is the first time his campaign has run any ads there.

Romney faces a tricky balancing act on discussing the state's auto industry after writing an op-ed in The New York Times in 2008 titled "Let Detroit go bankrupt." Most conservatives opposed the bailout at the time, but in Michigan even some conservatives now believe it saved the industry.

Earlier Tuesday, Romney authored another op-ed — this time published in a Detroit newspaper — seeking to explain his position on the industry and attack President Obama.

Watch the ad here: