AP

ABC News' Michael Falcone reports:

WAUKESHA, Wis. - Rick Santorum said on Monday that he was "feeling like we might pull off an upset" in Tuesday's Wisconsin primary, and if he does it will be largely due to the support of voters like Sanna Huebschmann.

"I'm hesitant with Romney only because he changes positions," Huebschmann said in an interview on Sunday at a bowling alley in Chilton, Wis. about an hour south of Green Bay. "Romney doesn't speak so well to an audience, doesn't get so passionate, doesn't connect."

Huebschmann, who wore a button with a photo of President Obama and the slogan: "Done. Jan 20. 2013," watched Santorum bowl a few frames. Although pledged to cast her ballot for Santorum on Tuesday, she said that if Mitt Romney ends up as her party's nominee she would support him.

The former Pennsylvania senator has been trailing in recent polls in the Badger State, but there are also indications that late-deciding voters are breaking for him in larger numbers than for Romney. Huebschmann said she was one of those who made up her mind during the final weekend before the primary.

An NBC News-Marist University poll taken last week showed Romney receiving the support of 40 percent of likely primary voters and Santorum with 33 percent. Seven percent of voters said they were undecided - a number equal to the margin separating the two Republican candidates.

Over the past two days Santorum has focused his campaign stops in rural northeastern areas of the state where he will need to do well if he has any hope of overtaking Romney, who has concentrated on the Milwaukee suburbs.

"Mitt Romney, I don't trust, especially because of Romneycare," said Robin, a Republican voter from Manitowoc who listened to Santorum's stump speech on Sunday. "I'm looking at Rick Santorum simply because he's a Reagan-type candidate."

Robin said she came to the conclusion that Romney would not "be a viable contender" against President Obama in the fall.

These Santorum supporters say they have not been swayed by the fact that many top Republican figures, including Wisconsin Sen. Ron Johnson and Rep. Paul Ryan, have closed ranks around Romney ahead of the primary.

Like other Republicans who have opposed Romney in primaries and caucuses from Iowa to Illinois, these Wisconsin voters cited the former Massachusetts governor's record on health care, his changing positions and what they see as his inability to relate to Americans, as their top concerns.

"I don't want to disparage Mitt by any means because I will vote for him if he gets the nomination," David Matasek of Mequon, Wis. said in an interview with ABC News. "I just don't connect with him on a personal level."

Matasek said he was sure Santorum was as electable against President Obama as Romney.

"I really believe he's a true conservative and his focus on the family," he said of the former Pennsylvania senator. "His positions on the economy, on energy are all consistent."

Another late decider, Dorothy Sievert, is exactly the kind of voter the Romney campaign needs to win over in large numbers on Tuesday. Sievert who lives about 30 miles south of Milwaukee in Mukwonago, Wis., said in the last few days she "kind of coalesced" around Romney.

"The Romneycare stuff did bother me in the beginning, but I also realized the health care issue on a state level is much different than on a national level," she said. "I know that he will repeal it, I have no doubt about that."

Sievert and other Wisconsinites who waited until the waning days of the primary here to choose a candidate seemed to be coming to terms with the fact that "none of these candidates are perfect."

Michael Best, a salesman from Pewaukee, Wis. - another Milwaukee suburb that should be a Romney stronghold - said he too was leaning toward the former Massachusetts governor.

"Electability trumps everything," Best said in an interview with ABC News, adding that he struggled to make up his mind, but finally concluded there is no such thing as a "perfect candidate."

"I wish we could take all three of them and mold one guy with all the best, but we can't do that," Best acknowledged. "The brilliant mind of Gingrich, the really conservative core values of Santorum, and the electability of Romney."