MESA, Ariz. -- Days before a pair of crucial primaries, Mitt Romney and Rick Santorum clashed Wednesday night in a testy debate that magnified small differences and underscored the big stakes in their neck-and-neck presidential fight.
The former Massachusetts governor was aggressive from the start, challenging Santorum's claims of fiscal prudence. Romney criticized Santorum for voting to raise the debt ceiling five times and repeatedly seeking earmarks -- money that lawmakers steer to specific home-state projects.
The former Pennsylvania senator defended the practice by saying that Congress has an important oversight role in shaping the federal budget. "Sometimes the president, the administration, doesn't get it right," Santorum said.
Romney, calling for a ban on earmarks, pounced with a reference to his stewardship of the troubled 2002 Olympics in Salt Lake City. "While I was fighting to save the Olympics, you were fighting to save the 'bridge to nowhere,' " he said, referring to the proposed crossing to a small Alaska island that became a symbol of government profligacy.
"You're entitled to your opinions," Santorum snapped. "You're not entitled to misrepresent the facts, and you're misrepresenting the facts. You don't know what you're talking about."
The exchange typified the evening. It was prickly, personal and seemed to reflect an eagerness to engage -- even when the issues were esoteric and the other candidates, Ron Paul and Newt Gingrich, were left to chime in from the sidelines.
Romney, the front-runner throughout most of the contest, was seeking to halt Santorum's momentum ahead of Tuesday's votes in Arizona and Michigan and, one week later, Super Tuesday, when more than a third of the delegates needed to clinch the GOP nomination will be at stake.
One of the more contentious and convoluted exchanges involved religious freedom and the sweeping health care law passed under President Barack Obama.
The four candidates were unanimous in condemning the administration's decision, since amended, to require religious employers to provide contraception in their employee insurance plans. Santorum went a step further, saying the health care program implemented under Romney in Massachusetts served as the model for Obama's plan -- including the contraception provision that Romney and others decried.
"The whole reason this issue is alive is Romneycare," Santorum asserted.
Romney responded by noting that Santorum endorsed him when he ran for president in 2008, after passage of the Massachusetts law, and insisted the only reason Obama's law passed was the vote of former Pennsylvania Sen. Arlen Specter, whom Santorum backed for re-election.
"So don't look at me," Romney taunted. "Look in the mirror."
Specter, a moderate Republican who switched parties and became a Democrat under Obama, has long been a pariah to many conservatives. Santorum backed him in a pitched 2004 campaign against then-Rep. Pat Toomey, the candidate favored by many on the right.
Santorum responded by saying he supported Specter because he promised, as chairman of the Senate Judiciary Committee, to support conservative appointees to the U.S. Supreme Court. "I did the right thing for our country," he said.
Santorum largely steered clear of the provocative statements that dominated his week. Rather than declaring that that government's role in public education is "anachronistic," he reiterated that he would like to see federal and state power over education returned to the local level.
"Look, I'm a homeschooling father of seven," he said, adding, "I know the importance of parental control of education, I know the importance of local control of education," he said.
The audience booed when the debate turned to the issue of contraception, a question raised by a viewer who emailed CNN's website and asked which of the candidates believed in birth control. No one answered directly.
Santorum spoke of the rising incidence of out-of-wedlock births and the difficult straits faced by children born to single mothers. "We hear this all time, 'So you cut spending, limit the government, everything will be fine.' No, everything's not going to be fine," Santorum said. "There are bigger problems at stake in America."
Paul, an obstetrician, argued that contraception was not to blame.
"The pill is there and, you know ... contributes, maybe," he said, "But the pills can't be blamed for the immorality of our society."
The debate, the 20th of the Republican contest and the first in nearly a month, came at a potentially pivotal moment in the race.
The last time the candidates gathered, in Florida, Romney was fending off a challenge from the onrushing former House Speaker Gingrich and hoping to clinch the nomination with a big win in the Sunshine State. But after a string of victories in Minnesota, Missouri and Colorado, Santorum rose as Romney's major challenger, turning Romney's native Michigan into a must-win for him.
Arizona, where Romney leads in polls, has seemed less important in the scheme of the race and the debate underscored its role; illegal immigration, an issue of special concern to Arizona, did not surface until more than halfway through the debate.
The candidates called for even more stringent moves than have been tried in the state, including construction of a massive wall along the length of the U.S.-Mexico border. "I think you see a model here in Arizona," Romney said, adding as president he would drop the federal lawsuits the Obama administration has filed to challenge the state's crackdown.
At one point, the debate's sharp tone was broken as the candidates were asked to describe themselves in a single word.
"Consistent," Paul barked out.
"Courage," Santorum said.
"Resolute," Romney replied.
"Cheerful," Gingrich said puckishly, drawing laughter and applause from the audience.