Last night's debate in Jacksonville featured a more aggressive Mitt Romney, who appears to have benefitted from debate coaching, a somewhat tired-looking Newt Gingrich, a sprightly Ron Paul, and Rick Santorum getting much more attention than usual. Scott Conroy of RCP:

...at the latest Republican faceoff here on Thursday, debate moderator Wolf Blitzer gave Santorum the first and last word of the night, and the candidate who is running a distant third here appeared up to the challenge of nudging himself back into the conversation in what has become a two-man narrative in the state.

Sen. Santorum used the debate to land shots on frontrunner Romney, arguably more impressively than Newt.

After Romney defended once again the universal health care plan that he enacted as governor, Santorum was ready to pounce with one of the most memorable exchanges of the night.

"What Gov. Romney just said is that government-run top-down medicine is working pretty well in Massachusetts and he supports it," Santorum said. "Now, think about what that means."

When Romney cut his opponent off and protested that the law in Massachusetts did not carry a government plan and was intended to eliminate free-riders from the system, Santorum did not give an inch.

"Just so I understand this, in Massachusetts, everybody is mandated as a condition of breathing in Massachusetts, to buy health insurance," Santorum said with a slightly bemused expression. "And if you don't, you have to pay a fine."

The exchange between Santorum and Romney continued for a few more minutes, as Gingrich and Ron Paul stood by and watched.

Jeffrey H. Anderson at the Weekly Standard Blog offers further details of the exchange:

Without having said how Romneycare differs from Obamacare, Romney concluded by saying, "We consider it very different than Obamacare." He then shifted his focus to Obamacare itself, saying, "If I were president, [on] day one I will take action to repeal Obamacare. It's bad medicine. It's bad economy. I'll repeal it."

He added, "I believe the people of each state should be able to craft programs that they feel are best for their people. I think ours is working pretty well."

Santorum pounced:

"What Governor Romney just said is that government-run top-down medicine is working pretty well in Massachusetts, and he supports it. Now, think about what that means - going up against Barack Obama...you are going to claim, well, top-down government-run medicine on the federal level doesn't work, and we should repeal it. And he's going to say, wait a minute, Governor. You just said that top-down government-run medicine in Massachusetts works well.

Santorum added, "Folks, we can't give this issue away in this election. It is about fundamental freedom."

For his part, Mitt Romney pressed Gingrich. Jim Rutenberg and Jeff Zeleny of the New York Times write:

...clearly prepared with reams of research, he frequently turned Mr. Gingrich's attacks back against him. When Mr. Gingrich pressed Mr. Romney for having investments in Fannie Mae, Freddie Mac and with Goldman Sachs, "which is today foreclosing on Floridians," Mr. Romney was ready with an attack of his own.

"Mr. Speaker, I know that sounds like an enormous revelation, but have you checked your own investments?" he asked. "You also have investments for mutual funds that also invest in Fannie Mae and Freddie Mac."

Effectively shut down, Mr. Gingrich turned grim and said meekly, "All right." (snip)

...Wolf Blitzer of CNN, effectively invited Mr. Gingrich to critique Mr. Romney's release this week of his tax returns, which disclosed that his blind trust included a Swiss bank account that was shut down in 2010.

"How about if the four of us agree for the rest of the evening we'll actually talk about issues that relate to governing America?" Mr. Gingrich responded when Mr. Blitzer asked him if he was satisfied that Mr. Romney was sufficiently transparent in releasing his tax returns.

But after Mr. Blitzer noted that Mr. Gingrich had made an issue of Mr. Romney's personal wealth earlier this week, Mr. Romney said sternly, "Wouldn't it be nice if people didn't make accusations somewhere else that they weren't willing to defend here?" Inviting a fight in which he used offense as defense, as he did many times during the course of the night, he told Mr. Gingrich, "I think it's important for people to make sure that we don't castigate individuals who've been successful."

Newt didn't have a good night, but it was not a disaster, to be sure. Guy Benson of Town Hall summarizes Newt's night:

The former House Speaker wasn't terrible tonight, but he came out flat in a format that usually works to his advantage.  As outlined above, he lost key points to Romney and failed to harness the energy of the crowd in his favor.  One significant developement came when Newt tried to defend his idea of establishing a lunar colony, even with a potential path to US statehood.  All three of his rivals shot the idea down as a misplaced priority in an era of high unemployment and myriad serious problems on this planet.  Gingrich parried weakly, if intriguingly, almost as if he was a professor tossing out an interesting big idea and running it up audience's flag pole.  Thought-provoking?  Yes.  Fiscally responsible and sensible in this context? Probably not.  Gingrich, of course, had several excellent answers.  His Israel/Palestine response was outstanding, detailed, and persuasive -- as was his response about religious liberty in America.  Religious Americans definitely sense their liberties and values are under assault by an aggressive secular minority, and Newt tapped into those feelings in a compelling way.  After the debate, Red State editor Erick Erickson said on CNN that Newt "lives and dies" by the debate and stated that Newt "lost Florida tonight."

Ron Paul presented his usual libertarian positions rather effectively. For example, when asked about immigration, he said that instead of spending money on the Afghanistan Pakistan border, use those resources on the US borders, to loud applause.  His most charming moment came in response to a question about his health, when he challenged the others to a 25 mile bike ride.