In a presidential primary season packed with debates, tonight’s could be the most critical for Mitt Romney.
Since he righted his campaign with robust debate performances and a strong primary win in Florida late last month, Romney has watched his momentum evaporate before a surprising surge from rival Rick Santorum.
Tonight’s debate in Mesa, Ariz., will be the last chance on a national stage for Romney to swing voters before Tuesday’s primaries in Arizona and Michigan and Super Tuesday’s 11 contests on March 6. Until recently, Romney was considered a prohibitive favorite in both Arizona and Michigan.
As part of his attempt to reinvigorate his candidacy, Romney is expected to try to turn the discussion tonight toward economic matters - his perceived strength - and away from the type of social issues that have been fueling Santorum’s run. Romney is planning a major economic address on Friday in Detroit, where he will offer new specifics on his tax policy and ideas for changes in entitlements. Campaigning in Michigan yesterday, he said he would propose a flatter, more broad-based tax system.
Joining Romney and Santorum tonight will be Newt Gingrich, whose candidacy has struggled for money and votes since Florida, and Representative Ron Paul of Texas, who will seek to capture a chunk of delegates in upcoming states that award their votes proportionally.
Santorum, too, faces increased pressure tonight.
“For Santorum, there’s going to be a lot of people giving him a hard look,’’ said Jeffrey Berry, professor of American politics at Tufts University. “He’s been discounted for so long as a fringe candidate that a lot of viewers don’t have a firm fix on him yet.’’
Santorum, a former Pennsylvania senator, has used his upset victories in Colorado, Minnesota, and Missouri this month to propel his candidacy nationally. Increasingly, Tea Party and evangelical voters are seeing him as the most viable alternative to Romney, according to recent polls. A Gallup poll released yesterday had Santorum up by 10 points nationally over Romney.
Romney remains slightly ahead in Arizona, according to a CNN/Time poll. But in Michigan, Romney and Santorum are running head to head. A loss for Romney in Michigan, which he won handily in 2008, could be devastating to his campaign.
The race has become increasingly negative, with attack ads both from campaigns and the super PACS supporting them. Yesterday, Paul’s campaign released an ad featuring a cartoonlike cutout of Santorum and attacking Santorum’s record in Congress, including his votes to raise the debt ceiling and to support the Medicare Part D prescription drug benefit without funding it.
Romney and a super PAC supporting him have also slammed Santorum for his fiscal record, particularly his requests for earmarks. Santorum, in his own ad, attacked Romney for negative campaigning.
Tonight, Romney is likely to continue to portray Santorum as a career Washington politician who favors government spending. Santorum will probably portray Romney as too liberal and too similar to Obama on such issues as health care.
In some of his most forceful remarks, Santorum yesterday denounced the compromise Obama recently announced to ease a rule requiring religiously affiliated organizations to pay for insurance plans that offer contraception.
“It was a phony accommodation,’’ he said. “It was an accommodation meant to do just that - to divide, not to accommodate sincerely held religious beliefs, but to trample those beliefs, because the government knows best how to run your life.
“Ladies and gentleman, this election is about foundational things. It is about the very nature of our country. It is about liberty. It is about whether we are going to be a free people,’’ he said.
Gingrich, a former House speaker, and Paul will try to prove they remain viable candidates, though Paul has yet to win a single state. Gingrich has recently focused on lowering gas prices through his energy policy, which he laid out in a new 28-minute online video. Paul has maintained the libertarian-leaning ideology he has espoused for years, focusing on his noninterventionist foreign policy and changes to the monetary system.
Illegal immigration may also be a hot issue in Arizona, home of a controversial bill cracking down on illegal immigrants. But Richard Herrera, associate professor of political science at Arizona State University, said the controversy has died down.
Herrera said he expects to see the candidates continue to use the same tactics they have in the last week - Santorum trying to motivate social and religious conservatives and Romney focusing on fiscal policy.
Herrera said Santorum’s rise in the polls over the last month is remarkable.
“He’s the candidate with momentum right now,’’ he said.
Globe staff reporter Michael Levenson contributed to this report. Shira Schoenberg can be reached at sschoenberg @globe.com.