The last four Republican presidential candidates in the last debate before the Michigan, Arizona and Super Sunday contests went at it in Mesa, Arizona. It was, to be blunt, a wipeout. Mitt Romney brought the heat and the oppo research and flattened Rick Santorum, getting the former Pennsylvania senator hot and defensive. It was also a good night for Newt Gingrich, who returned to his professorial role. And Ron Paul, for once, was a model of common sense, at least when it came to the federal government and contraception.

Romney’s staff must have worked overtime to come up with a raft of data on Santorum. Romney hit Santorum on subsidies for the airline industry and the steel industry. Romney went after Santorum for earmarks. Santorum seemed to get lost in the weeds, sounding defensive and at times falling into Senate-ese. The discussion chewed up a chunk of time and finally left us with the impression he was a Washington politician. He lost in those minutes the image of being a bold conservative. Suddenly he was another weasely senator who voted for a bunch of expensive programs.

Romney bludgeoned Santorum on his endorsement of former Sen. Arlen Specter (R-Penn.), who was eventually the 60th vote for Obamacare. With help from Paul, Romney also managed to tie Santorum up in knots on his votes, which included funding for Planned Parenthood.

A much as on substance, Romney won on temperament. He was precise and calm. Santorum at times was obviously mad, pointing his finger and jabbing the air with his pencil.

Paul certainly did his part to dismantle Santorum. Asked why he ran an ad saying Santorum is a fake, Paul replied with a smile, “Because he is a fake.” Paul chided Santorum for bragging that his spending record was better than that of other members of Congress. And Paul told Santorum that he was wrong that birth control causes immoral behavior, making an analogy to the Second Amendment argument that guns don’t kill people. Santorum was reduced to pleading that he wanted to talk about contraception but not do anything as a policy matter. (But if it is really such a great threat to society, why not?) When Santorum confessed to being a good team player for George W. Bush’s No Child Left Behind, Paul zapped him for being too good a team player. Hitting Santorum on his strong suit — his purported conservative courage — was a masterstroke. Alas, Paul also reverted to his bizarre foreign policy, evidencing great sympathy for Iran.

Even when not attacking Santorum, Romney was on his game. Romney did a good job defending his position on the auto bailout, weaving an all-out attack on the United Auto Workers. He gave a ringing defense of women in the military, pointing out that 100 or more had died serving in Afghanistan and that military commanders had supported opening up jobs to women. He gave an around-the-world critique of Obama’s foreign policy failures and declared that Obama’s greatest failure was his failure to stop Iran’s nuclear program and support the Green Movement. On education, he channeled New Jersey Gov. Chris Christie (R) by going after teacher unions and touting his own role in state education reform.

Gingrich also had a good night, appearing sunnier than in the past. He took a swing at the media for a double standard on social issues. He used the word “cheerful” when asked to describe himself in one word. He gave a boffo answer on standing with Israel and preventing Iran from getting the bomb. His riff on “self-esteem” in schooling was classic Newt.

As for Santorum, the fight seemed to go out of him after being on the defense for the first hour or so of the debate. He was left to agree with both Gingrich and Romney on Israel and Iran. He essentially folded his tent on opposing women in combat, saying that he only had “concerns” but would defer to the commanders. When responding to a question on No Child Left Behind, he said it was against the principles he stood for. He admitted error, but it sounded rather wimpy. Most critical, however, were his failures to get out his affirmative message, to explain his economic plan and to sell his electability. He was on defense, and his opposition ran up the score.

Astoundingly, no candidate successfully laid into Romney on Romneycare, on his position on gay marriage, or on abortion — or on much of anything regarding to his gubernatorial record.

Finally, after getting bashed by Gingrich in South Carolina, John King held his own against the boo-birds when he asked about contraception. He smartly avoided the “Satan” topic and kept the debate moving. He gets special credit for devoting significant time to foreign policy.

Winners: Romney, Gingrich

Loser: Santorum