LANSING -- GOP presidential candidate Rick Santorum is clinging to his lead in the Michigan primary.

News 10's latest "Voice of the Voter" poll, conducted by EPIC-MRA, shows Santorum with a 37 percent to 34 percent lead over rival Mitt Romney, though that's within the margin of error.

Ron Paul (10 percent) and Newt Gingrich (7 percent) are trailing badly, while 12 percent of the respondents are undecided.

But here's the catch.

Just 54 percent of respondents say their decision is set in stone, while 45 percent say their decision could change before Tuesday's vote.

"That is incredibly high," says EPIC-MRA pollster Bernie Porn. "You have a lot of volatility and a lot of potential fluidity over the next few days."

When you count just the respondents who say they'll definitely vote this Tuesday, Santorum takes a 9 percent edge.

The former Pennsylvania Senator has gained that lead by playing up his pro-manufacturing policies and social conservatism -- both of which play well among Michigan's tea partiers, who make up a large share of the Republican vote.

Romney, though, has staged a bit of a comeback and still has the money and time to convince Republicans that he's their guy.

"He needs to appeal to that Tea Party crowd in a more direct way than he has so far," Porn says.

Romney's favorability rating also trails Santorum, 62 to 58.

Seventy-three percent of the poll respondents are Republicans; 10 percent are Democrats.