Has a Mitt Romney surge begun in Michigan?  A week ago, PPP had Rick Santorum up by fifteen points in Romney’s home state.  In their new poll, PPP puts Romney back only four — although Santorum hasn’t actually lost any support:

The Republican race for President in Michigan has tightened considerably over the last week, with what was a 15 point lead for Rick Santorum down to 4. He leads with 37% to 33% for Mitt Romney, 15% for Ron Paul, and 10% for Newt Gingrich.

The tightening over the last week is much more a function of Romney gaining than Santorum falling. Santorum’s favorability spread of 67/23 has seen no change since our last poll, and his share of the vote has dropped only 2 points from 39% to 37%. Romney meanwhile has seen his net favorability improve 10 points from +10 (49/39) to +20 (55/35) and his vote share go from 24% to 33%.

What we’re seeing in Michigan is a very different story from Florida where Romney surged by effectively destroying his opponent’s image- here Romney’s gains have more to do with building himself up.

It’s not for lack of trying that the negative campaigning hasn’t made much of a dent in Santorum’s standing.  My inbox gets at least one or two hits on Santorum from Team Romney every day, and Romney’s super-PAC has run some negative ads in Michigan against Santorum.  The impact from those efforts has been minimal; Santorum still rates higher with voters on representing their own views, for instance (48%, compared to 32% for Romney), and almost two-thirds (62%) think Santorum’s in the Republican mainstream; only 42% say that about Romney, with 37% believing he’s too liberal.

Romney seems to be winning support from the rest of the field by promoting himself rather than attacking his main competition.  He has spent a lot of time in Michigan emphasizing his ties to the state (ineffectually, according to PPP, with only 29% buying that argument), and making the case that his executive experience and turnaround capabilities are what is needed in this election.  Even his opposition to the automaker bailouts isn’t hurting Romney (only 27% think that’s a negative, and 35% don’t care about it at all); voters seem to be rethinking Romney on the basis of his approach to the economy.

The news isn’t all bad for Santorum.  First, his support hasn’t come down at all — Romney has picked up support from elsewhere.  When Newt Gingrich gets removed from the equation, Santorum leads by nine points, 42/33, which means that Romney has gotten about all of the Gingrich support he’s going to get in Michigan, and the rest would tilt to Santorum.  Almost half of the respondents think Gingrich should drop out (47/40), although that is extremely unlikely with Sheldon Adelson’s new $10 million donation to Gingrich’s super-PAC.

Last week, I noted that this state has now become critical to both Romney and Santorum.  Romney should never have had to work this hard to defend his home state. Santorum’s clear lead last week raised expectations for his performance one week before Super Tuesday from the point where a decent second place would have been sufficient.  One of these men has to lose in Michigan, and whoever finishes second will lose significant standing in the race one week before Super Tuesday.