A Loss in Michigan would be a stake in the heart of Romney. And a lot of Republicans think it is time for GIngrich to hang it up. If he did, Santorum would be up big.

PPP: Santorum 37, Romney 33 in Michigan

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.

Groups Santorum has double digit leads with include Protestants (up 47-30), union members (up 43-23), Evangelicals (up 51-24), Tea Partiers (up 55-20), ‘very conservative’ voters (up 54-23), and men (up 40-28).

Romney is leading the field with women (38-34), seniors (42-34), moderates (35-24), ‘somewhat conservative’ voters (40-34), and Catholics (43-31).

Newt Gingrich’s continued presence in the race is helping Romney a lot. If he dropped 45% of his supporters would go to Santorum, compared to only 29% for Romney and it would push Santorum’s lead over Romney up to 42-33. 47% of primary voters think Gingrich should drop out while only 40% believe he should continue on, but he’s certainly not showing any indication he’ll leave.

Santorum’s advantage over Romney seems to be a reflection of voters being more comfortable with where he is ideologically. 48% of voters think Santorum has more similar beliefs to them, compared to only 32% who pick Romney on that question. 63% of primary voters think Santorum’s views are ‘about right’ compared to only 42% who say that for Romney. 37% believe that Romney is ‘too liberal.’

I agree with Politico that this poll is much more in line with other polling in the state and so is not really indicative of falling Santorum support. It is a tight race and Santorum has the opportunity to really stagger Romney and maybe even knock him down. And yes, I wish Gingrich would just get out already as I believe he has had his last surge.

If Santorum knocks Romney down in Michigan, he might not get back up again.