Once up by 15 percentage points over Romney, Santorum now had a 37 percent-to-33 percent lead over Romney in his home state, with 15 percent saying they favor U.S. Rep. Ron Paul and 10 percent saying they support former House Speaker Newt Gingrich, a Public Policy Polling survey released Sunday indicated.
Public Policy Polling said the turnaround was more because Romney, the former Massachusetts governor who has roots in Michigan, has seen his favorably number rise rather than Santorum, a former U.S. senator from Pennsylvania, falling. Santorum's favorability number of 67 hasn't changed while Romney's favorability number rose to 55.
Santorum enjoyed double-digit support among Protestants, union members, evangelicals, Tea Party movement supporters, "very conservative" voters and men.
Romney led with women, seniors, moderates, "somewhat conservative" voters and Catholics.
Thirty-six percent of voters said they could still change their minds by next week's primary.
Results are based on telephone surveys of 602 likely Republican primary voters Friday through Sunday. The margin of error is 4 percentage points.