Romney goes all native son:
Weigel offers a short history of the "driving ad":
The new ad from team Romney puts the candidate behind the wheel in Livonia, Mich., thinking big and talking sad about the state he grew up in. This adds to a rich tradition of ads that feature Candidates Driving Around and Learning Things. The man best identified with the driving ad is Scott Brown, who tried, and succeeded, to turn his truck into an icon. …
A campaign flyer celebrates Mitt's long-awaited homecoming:

Last night we mentioned that Michigan may be "do or die" for Romney. Jim Geraghty has more on what's at stake:
Romney began his career there; his father, George Romney, was a two-term governor and successful auto executive there. Of course, this factor is easily overstated; roughly 65 percent of Michiganders were not alive when Romney was last governor, in 1969. What’s more, Michigan’s population was estimated at 10,002,486 in 2008 and 9,876,187 in 2011, meaning that while the Michigan exodus has slowed in recent years, some of Romney’s backers from four years ago may not be around this cycle. The PPP survey notes that only 26 percent of primary voters think of Romney as a Michigander (interestingly, 33 percent of Romney backers don’t consider him to be one).
Here's the latest from Santorum's campaign:
Michael Brendan Dougherty praises the ad's cheeriness. But as Zeke Miller notes, we've basically seen this one before. Previous Ad War Updates here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here and here.