Rick Santorum has managed to parlay his three-state sweep earlier this month into strong polling in the two upcoming GOP primary contests in Arizona and Michigan. A Santorum win next Tuesday in either state could propel the GOP nomination fight deep into the spring.

The former senator seized the momentum by unexpectedly winning caucuses in Minnesota, Colorado and Missouri on Feb. 7. The sweep was a surprise as the polling leading up to those three contests only showed Santorum with a chance of winning two of them. Romney had a double-digit lead in Colorado, where he’d won in 2008.

Now, there’s less chance for a surprise in Arizona and Michigan because there continues to be substantial polling done in both states. Romney had been ahead – Rasmussen had Romney holding a 15-point lead in Michigan and a 24-point lead in Arizona in the first week of February, but that changed after Santorum’s recent victories.

The latest polling shows Romney’s support has eroded substantially. In Arizona, the former Massachusetts governor maintains his lead but the margin has shrunk from 24 points to between 3 and 10 percentage points, depending on the poll. Public Policy Polling has Romney up 3, CNN has him up 4, and Rasmussen has him at plus 8. WeAskAmerica has him up by 10.

More concerning for the Romney camp, though, are the recent polls coming out of Michigan, the state where his father served as governor. Mitchell Research/Rosetta Stone and NBC News currently have Romney leading in Michigan by 2 points, while Rasmussen and PPP have Santorum with a 4-point edge. Despite these differences, each result falls within the respective poll’s margin of error and so cannot be distinguished from a statistical tie.

Some observers have pointed to Romney’s opposition to the auto bailout, highlighted by his infamously titled 2008 New York Times op-ed “Let Detroit Go Bankrupt,” as the major driver of his declining popularity in Michigan. But recent polls don’t back that up. PPP finds that 34 percent of likely Michigan Republican primary voters are more likely to vote for a candidate who opposed the auto bailout, while only 27 percent consider opposition a negative and 35 percent say it does not make a difference either way.

A recent Detroit News poll similarly found that roughly 50 percent of Republican primary voters in Michigan say that anti-bailout positions will not influence their vote.

Still, Romney’s position on the bailout—and Santorum’s, as they’re basically indistinguishable—could have serious ramifications this November. Indeed, when all voters are included in the latest PPP polling, a majority (52 percent) support the auto bailout while just 36 percent oppose it.

Regardless of the impact his stance on the auto bailout will have on November, Romney is focused on February and has managed to increase his favorability in Michigan to 55 percent, up from 49 percent a week ago. This jump may allow him to sweat out a win next week, but a great deal can happen between now and Tuesday. Close results in Michigan and Arizona could legitimize Santorum as the credible alternative to Romney heading into the all-important Super Tuesday contests on March 6.

Stefan Hankin is founder and president of Lincoln Park Strategies, a Washington D.C.-based public opinion firm. Follow him on Twitter at @LPStrategies