Some thoughts about tonight's debate:
Though there wasn't a massive pile-on as in the last debate, Perry continued to lose ground, and most of his wounds were self-inflicted. The shadow of George W. Bush loomed larger over Rick Perry tonight. Perry's verbal stumbles and with-me-or-you're-a-bigot tone on immigration issues might have reminded activists and conservative politicos a little too much of the former Republican occupant of the White House. If Perry seems like George W. Bush Part II, he won't be able to clinch the GOP nomination, let alone the presidency. Moreover, his attacks on Romney often fell flat or wandered. Perry needs to sharpen his approach if he wants to gain here.
Romney followed his usual strategy of survivor in this debate: he didn't let anything get to him and didn't indulge in political napalm. He just kept insisting on his message. Romney did seem to have a few moments of sputtering, though. They might have added to his sense of authenticity, but they also made him seem less steady on his rhetorical feet. Romney's survivor strategy has paid off in the past couple debates. He's blunted the rise of Rick Perry and kept the Texas governor from running away with the race this early. Time will tell if this will allow him to wrest away the primary polling lead.
Santorum stood out in this debate. He had few striking exchanges (on immigration with Perry and foreign policy with Huntsman). I don't know how much these debate performances will translate into polling benefits for him, but he's definitely keeping his place at the table.
Gingrich is still plowing along. His comity tactics seem to help give his ideas a stage at these debates---and finding that stage may be more of a priority for Gingrich at the moment than the GOP nomination.
Johnson had a good line, perhaps good enough for him to stay in the debates. Cain had some other good points. I think Huntsman still wanders sometimes, but he seems to be keeping his campaign viable. Ron Paul was himself. Bachmann struggled to find her voice again.