Santorum planned to host his election watch party Tuesday in western Pennsylvania — an indication he may not feel good about his chances in Wisconsin.
Still, cultural conservatives have struggled to embrace Romney.
On average, in states where exit or entrance polls have been conducted, white evangelical conservatives have made up about half of the GOP primary electorate.
Romney did not win in any of the eight states where they were a majority of voters, and he carried evangelicals themselves in just five states: New Hampshire, Nevada, Massachusetts, Virginia and Vermont.
Outside of those states, Romney has won on average 28 percent of votes among evangelicals, compared with a 37 percent average support for Santorum.
Even in states Romney won after hard-fought campaigns, such as Michigan and Ohio, he has struggled to appeal to white evangelicals. He trailed Santorum among evangelicals by 16 percentage points in Michigan, 17 points in Ohio.
Several primary voters at the forum Saturday voiced reservations about Romney, but said they would likely support him if he's the nominee.
"If he turns out to be the candidate, you bet I'll be behind him," Mary Ruth Gobek of Waukesha said. "But there's that hesitation, that question mark."
Romney sought to answer questions by heralding the recent endorsements by an array of Republican establishment and conservative leaders. Among them were Florida Sen. Marco Rubio and Utah Sen. Mike Bell, both tea party favorites. In Wisconsin, Romney was introduced by House Budget Committee chairman Rep. Paul Ryan, a local GOP hero and a rising national star. Ryan endorsed Romney Friday.
"I think there comes a point where this primary can become counterproductive," Ryan told the audience. "I think we need to coalesce around the person we think is going to be the best president and who gives us the best chance of realizing this vision."
Associated Press Writer Beth Fouhy in Milwaukee and AP Deputy Director of Polling Jennifer Agiesta in Washington contributed to this report.
Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.