3. Herman Cain can't laugh off everything. The first segment of the debate was devoted to a round-robin bash-fest of Cain's "9-9-9" tax plan, and Cain's glib denials that it would have the effects independent experts contend -- like raising taxes on a lot of people, chiefly those who can least afford it -- finally started to fall flat. After that, Cain abruptly ceased to be a focal point as the debate's center of gravity shifted to Romney.

The last portion of the debate was much worse for Cain as the topic switched to his weakest subject, foreign policy. He got badly tangled up in the question of whether he would negotiate with al-Qaeda for the release of prisoners from Guantanamo, trying to avoid backing down from previously saying that he would while also categorically stating he wouldn't ever negotiate with terrorists. "I would never agree to letting hostages in Guantanamo Bay go," he stumbled at one point. (After the debate, he told reporters he'd misspoken -- obviously.) Michele Bachmann called him "naive."

Despite Cain's technical claim to front-runner status -- every poll in the last week or so has shown him statistically tying or surpassing Romney -- it's clear his rivals don't believe he has the staying power to make him worth really working to tear down. They're pretty sure he can do that on his own.

4. Everybody's a little punch-drunk at this point. This debate was the most contentious we've seen yet, a melee of shocking nastiness and rancor. Some in the GOP fretted that the ultimate effect would be to damage the party as a whole as the candidates seemed to tear each other apart at the expense of their ultimate goal -- beating President Obama in the general election. Several speculated that Jon Huntsman, who opted out of the debate in a show of solidarity with New Hampshire, might have come out of the night the best of anyone.

These candidates have met for five debates in six weeks. It's probably a good thing that they'll be spending the next three weeks apart. We could all use a break.

5. There's life in the old Newt yet. Gingrich's shtick in these debates has been predictable: go after the moderators and the media and position himself as the uniter in a divisive world. (It helps that few have bothered to attack him.) Nonetheless, it's working for him, and Gingrich seemed to get the most airtime of the candidates not named Romney, Perry or Cain. He hit it out of the park with his answer to a question about how Republicans can appeal to Latino voters: "I think we have to have the same message for every American of every ethnic background that we want to make America work again."

Gingrich may have lost some local support, however, when he came out in favor of the proposed Yucca Mountain nuclear waste repository, which would store the nation's spent nuclear material less than 100 miles outside Las Vegas. That might not be a deal-breaker with Nevada voters primarily concerned about the economy -- John McCain supported Yucca and so did George W. Bush before him. But it won't help.