MESA, Ariz. (AP) -- Rick Santorum is looking for another upset or two, while Mitt Romney is hoping to keep his leading rival at bay in the run-up to the 20th debate of the race for the Republican presidential nomination.
"I wouldn't be here if I didn't think I could do well," the former Pennsylvania senator told supporters Tuesday after arriving ahead of any of his rivals for pre-debate campaigning in Arizona, a state that has long been assumed safe for Romney.
Both Arizona and Michigan hold primaries on Feb. 28, but until recently, at least, the similarities seemed to end there.
Polls have long shown Romney with a solid lead in Arizona, where all of the 29 delegates at stake are reserved for the top vote-getter in the primary. As a result, neither he, Santorum, Newt Gingrich nor Ron Paul has devoted much time to the state.
A surging Rick Santorum is running even with Mitt Romney atop the Republican presidential field, but neither candidate is faring well against President Barack Obama eight months before Americans vote, a new survey shows.
Meantime, an Associated Press-GfK poll shows that President Barack Obama tops 50 percent support when matched against each of the four GOP candidates and holds a significant lead over each of them.
In Arizona, television ads have been scarce. None of the candidates has run commercials, and Restore Our Growth, an outside group that has played a major role in Romney's success so far in the campaign, is the only organization to pay for ads.
In Michigan, by contrast, Romney's lead in public and private surveys began eroding earlier this month when Santorum won upset victories in caucuses in Minnesota and Colorado and a non-binding primary in Missouri on a single night. Now the one-time front-runner campaigns as though he is behind.
Not surprisingly, Romney, Santorum and their allies have poured money into television ads in Michigan - about $5 million combined, with additions made Tuesday for the race's final week.
While Wednesday's debate is in Arizona, the stakes are heightened because some previous encounters have had an impact far beyond the state where they were held.
Most notably, former Texas Gov. Rick Perry never recovered from his failure to recall the third of three federal agencies he wanted to abolish. His lapse came in a debate in Michigan last November.
And Romney righted his campaign a month ago when he excelled in a pair of Florida debates after losing the South Carolina primary to Gingrich.
Romney campaigned in Michigan on Tuesday, and was pulled into a discussion of social issues by questioners at a town-hall style rally in Shelby Township.
Asked how he would defend religious liberty, he said Obama's administration has "fought against religion" and sought to substitute a secular agenda for one grounded in faith.
"Unfortunately, possibly because of the people the president hangs around with, and their agenda, their secular agenda - they have fought against religion," he said.
Obama's campaign seized on the characterization, calling Romney's comments disgraceful and likening them to recent comments by Santorum. The former Pennsylvania senator said recently the president holds a "phony theology," then insisted he wasn't attacking the president's faith, but his environmental views.
Republicans have accused Obama of violating religious liberties when the administration recently announced that except for churches, most employers would be required to make birth control available as an insurance benefit as part of the health care overhaul Congress passed in 2010. The White House backtracked, but not enough to satisfy conservatives.
Romney, who has had trouble winning the votes of tea party advocates, said they should be in his corner.
"I think the tea party would find it very interesting that Rick Santorum voted to raise the debt ceiling five times without getting compensating reductions in spending," Romney said, echoing the campaign ads his campaign and his allies are airing in Michigan.
Two thousand miles away, Santorum was cheered by a survey that showed a tighter-than-expected race in Arizona. He was repeatedly applauded during an appearance at a Lincoln Day luncheon held by the Maricopa County Republican Party.
"You can speak loudly on Tuesday that you want someone who's going to stand up and fight the insiders, fight the establishment, someone who has a track record of doing it," he said.
His reception was even better several hours later at a campaign rally.
Santorum "is just rock solid. He's sincere, honest," said Mary Muir, who said the rally was the first political event she has attended in 50 years.
Rich Kulok, 73, of Mesa, who also attended, said he was solidly for Santorum.
"I believe in the things he's saying," said Kulok, who worked in management and construction before retiring. "I'm dead set against abortion." He said Santorum "seems more genuine than the other guys."
"I think Romney will tell you anything you want to hear, depending on what city you're in," he said.
Gingrich has scarcely been a factor in either Michigan or Arizona, except indirectly.
His decision not to campaign in Michigan so far has allowed Santorum a chance to compete against Romney without also having to fend off a rival for the votes of conservatives.
Paul, though, has weighed in against Santorum.
He began running a new ad Tuesday that challenges Santorum's claim that he is a conservative on spending issues. It also notes the former senator voted to raise the debt limit five times, and says Santorum supported legislation that created a prescription drug benefit under Medicare.
Associated Press writers Charles Babington and Kasie Hunt contributed to this story.