A new poll shows Mitt Romney closing the gap on Rick Santorum a week ahead of Michigan's pivotal GOP presidential primary.

The latest survey from Public Policy Polling shows Rick Santorum leading with 37 percent support of likely Republican voters, ahead of Romney, with 33 percent. 


Texas Rep. Ron Paul is in third place with 15 percent and former House Speaker Newt Gingrich (Ga.) trails with 10 percent.

Santorum's four-point lead has been whittled down from his 15-point edge in a PPP poll last week.

Romney, the presumptive GOP front-runner, was expected to win easily in the state, but Santorum surged ahead in Michigan and nationally after pulling off a trifecta of upset victories in GOP contests in early February.

“Rick Santorum continues to have the lead in Michigan, but momentum is now on Mitt Romney’s side,” said President of Public Policy Polling Dean Debnam in a statement.

“Romney’s supporters are also more committed than Santorum’s, so there’s reason to believe this could get even closer in the final week of the campaign,” added Debnam.

Santorum holds a double-digit lead among evangelicals in the state, with 51 percent support to 24 percent. Among Tea Party supporters, he holds a similar edge, up 35 points with 55 percent to 20 percent for Romney.

Romney holds an edge among women voters 38 to 34 percent, however, and among self-described moderates with 35 percent support to 24 percent.

Santorum also wins among union members, up 43 percent to 23 percent. The former Pennsylvania senator has hit Romney for opposing the federal bailout of GM and Chrysler.

Yet the poll also finds that Romney's stance on the bailout has not hurt him overall with GOP voters. Thirty-four percent say they are more likely to vote for someone opposed to the government aid for the auto industry while 27 percent believe Romney's opposition is a negative.

The survey suggests that Gingrich's presence in the race is helping to bolster Romney. Forty-five percent of Gingrich supporters say that if the former Speaker dropped out of the race they would back Santorum. Only 29 percent of Gingrich backers would switch their support to Romney. A Gingrich exit would extend Santorum's lead to 42 percent to 33 percent.

While Romney still holds the edge in fundraising and organization, a loss in Michigan, coming one week before the key Super Tuesday primary contests, would be a strong setback to his campaign.

Santorum has attempted to downplay expectations, publicly stating that he would be pleased with a “strong second” place showing.

Romney has said that a loss in the state “won’t happen.” He grew up in the state, where his father also served as governor. 

Romney won the state in 2008, besting eventual GOP nominee Sen. John McCainJohn Sidney McCainBiden steps onto global stage with high-stakes UN speech Biden falters in pledge to strengthen US alliances 20 years after 9/11, US foreign policy still struggles for balance MORE (Ariz.).

The poll was conducted from Feb. 17-19 and has a four-point margin of error.