Mesa, Arizona (CNN) -- The four GOP presidential candidates had one last chance to state their case in front of the nation before Tuesday's primaries in Arizona and Michigan. Did one candidate stand out from the rest? Here are five things we learned from the CNN Arizona Republican Presidential Debate.
Santorum weighed down by Washington
It wasn't just that Romney and Ron Paul pressed him on his past support for earmarks, the Title X family planning program, the 'No Child Left Behind' education bill and his endorsement of moderate Republican Senator Arlen Specter over conservative Pat Toomey in the 2004 Pennsylania Senate primary.
Santorum made matters worse for himself by aggressively defending his Beltway votes.
He said he was "proud" to stand up for earmarks -- which many conservatives view as wasteful government spending -- after being elected to the House in 1990 and then to the Senate in 1994.
"Congress has a role of allocating resources when they think the administration has it wrong," Santorum said. "I defended that at the time. I'm proud I defended it at the time, because I think they did make mistakes. I do believe there was abuse, and I said we should stop it, and as president I would oppose earmarks."
His reputation probably wasn't helped by the fact that Google searches for the word "earmark" spiked dramatically during the debate, soaring upward by 2300%.
Santorum's explanation of his vote for 'No Child Left Behind' was even more complicating.
"I have to admit, I voted for that," he said. "It was against the principles I believed in, but, you know, when you're part of the team, sometimes you take one for the team, for the leader, and I made a mistake."
His comment drew boos from the crowd, but Santorum pushed forward.
"You know, politics is a team sport, folks," he said. "And sometimes you've got to rally together and do something."
To some conservatives, it may have sounded like Santorum was admitting to being part of the big government problem during the George W. Bush administration.
Santorum's labored defense of his Capitol Hill resume not only reinforced the accusation that he is a tainted Washington insider. It also undermined the central theme of his candidacy, that he is the only true conservative in the Republican race.
Santorum's defiance has its limits
Santorum seems incapable of defending his record without going into extensive and sometimes problematic detail, often with a hint of annoyance. It's not a new phenomenon.
When pressed about his record on the campaign trail, Santorum seems to relish verbal combat and defiantly spars with questioners, as his infamous January back-and-forth over same-sex marriage with college students in New Hampshire demonstrated.
"I'll defend everything I say," Santorum told reporters Wednesday after a rally in Phoenix.
But now that he's in the spotlight as the national Republican frontrunner, Santorum is struggling to stick to the campaign playbook that says a candidate should deliver concise answers and move on.
Santorum's senior adviser John Brabender said his candidate has trouble letting some accusations go unanswered.
"The question is, should he just be fighting back against Romney, or should he be explaining his record," Brabender said. "It is his record, and I think he feels like he has a responsibility to defend it."
Romney was happy to let him do that on Wednesday.
Romney still tacking right
Mitt Romney is no longer playing it safe when it comes to debates, framing his answers carefully with an eye on the general election.
Just over a week after declaring himself "severely conservative" in a major address to party activists in Washington, the former Massachusetts governor made a similar argument in Mesa.
"Severe, strict," Romney said when asked what he meant by his "severely" line. "I was, without question, a conservative governor in my state."
Romney framed his conservatism mostly in fiscal terms, saying he cut taxes 19 times and balanced the budget (even though he also raised some taxes and was required by state law to balance the budget).
However, Romney also highlighted socially conservative positions he took as governor, and said he battled with the Democratic-controlled legislature over issues like abortion, embryonic stem cell research and immigration.
Romney also won applause at President Barack Obama's campaign headquarters in Chicago when he called Arizona's tough immigration law "a model" for the rest of the nation.
He was talking specifically to an employment verification system included in the Arizona law, but Democrats will almost certainly use the remark as a cudgel against him in the general election if he is the Republican nominee as they seek to drive a wedge between the GOP and Hispanics, who voted for Obama over John McCain by a 67%-31% margin in 2008.
Romney campaign advisers exuded confidence after the debate, clearly pleased that Santorum decided to dig in and aggressively defend his record in Washington before a national television audience.
How confident were they?
Romney message maven Stuart Stevens guaranteed a win next Tuesday in Michigan, where polls show the race essentially tied between Romney and Santorum.
"We are going to win Michigan," Stevens told reporters in the spin room. "We are going to win Michigan."
Stevens also dismissed as a "parlor game" the chatter among some Washington insiders that a savior candidate might swoop in at the Republican National Convention in Tampa and rescue the party from doom in November.
"I think it's what we believe when it's impossible to believe in Santa Claus anymore," Stevens said of the contested convention talk. "This party has a great candidate, Mitt Romney. And you saw tonight, Mitt Romney is ready to be president from day one."
'Cheerful' Gingrich scores
Gingrich demonstrated that he's at his best when the pressure is off.
No longer the embattled GOP frontrunner taking fire from all sides, the Gingrich who showed up Wednesday resembled the loose and free-wheeling candidate he was last summer, when his cash-starved campaign was left for dead and relying on debates for free media exposure.
Though he couldn't resist a shot at the "elite media" early on for holding Obama and Republicans to different standards on social issues, Gingrich mostly shied away from cheap applause lines.
Instead, he stayed above the fray and outlined his ideas about energy, education and the auto industry with an upbeat air of confidence and authority.
Asked to describe himself in one word, the sometimes-surly candidate went with "cheerful."
"Newt has been criticized from time to time about being too strident," said Texas Gov. Rick Perry. "Tonight you saw Newt Gingrich, I think, channeling Ronald Reagan by saying the word that described him best was 'cheerful.' He truly is a cheerful warrior."
A third Gingrich surge seems like a dim prospect before Super Tuesday on March 6, but the former House Speaker reminded viewers Thursday that he deserves a seat at the Republican table for at least the next two weeks.