Former Gov. Mitt Romney found himself on the defensive as he never has been before. His health-care plan in Massachusetts finally got a real going-over, with Sen. Rick Santorum leading the way. Santorum was an important player throughout the discussion, and this has to give him a bump -- in attention, if not in the polls.

For the most part, Romney was fluid and fluent, as is his habit. But I thought the particularly bitter exchange he had with Perry, over whether Romney had hired an illegal immigrant, hurt Romney more than Perry. There was petulance and perhaps a trace of arrogance in the way Romney kept badgering Perry. “It’s been a tough couple of debates for Rick” and “You have a problem with letting people finish speaking” are Romney lines that will get played over and over, and I don’t think they came off well. In truth, neither Romney nor Perry looked great when they went into junkyard-dog mode, but it may be a net win for Perry, because he put himself on the same level as Romney. But on the question of Mormonism and the religious faith of politicians, Romney’s answer was very good, while Perry’s response at times came close to incoherence.

Herman Cain was the punching bag at the beginning of the debate, and while he stayed amiable, his 9-9-9 plan didn’t survive the scrutiny very well. Here again, Santorum played a key role. Cain simply can’t fend off the charge that his national sales tax would be added to state sales taxes -- because the charge is true. During the argument about 9-9-9, Perry shrewdly made a point of shouting out to voters in New Hampshire, which has neither a sales nor an income tax. Romney was effective on this point, too. A hunch: Cain will take a hit in the polls and some of his support may go back to Perry, where it appears to have come from.

Newt Gingrich looked positively statesmanlike complaining about all the bickering, and it was entertaining to watch the former Speaker attack Washington (which includes the Republican House of Representatives) for being “stupid” in the way it has been dealing with the budget.

Michele Bachmann has used the same lines in one debate after another. She did nothing (that I could see anyway) to stop her ongoing fade-out.

The fact that Santorum emerged, that Cain and Romney came under attack, and that Perry and Romney engaged in such bitter exchanges suggests that former Utah Gov. Jon Huntsman made a big mistake in skipping the Las Vegas debate. This could have been his moment to rise above the field. The others gave him an opening, but he wasn’t there to take advantage of it.

All of which suggests that one winner tonight was President Obama. The fact that Perry may have worked his way back into the mix and the likelihood that Romney and Perry will make life miserable for each other can only help the president. The candidates weren’t competing with each other to have the best attack lines against Obama to nearly the degree they had in the earlier encounters. Their assaults on each other will make the news, which means their anti-Obama remarks will fall to the cutting room floor -- or whatever the proper metaphor is for our digital age.

Oh, yes, and I do hope Perry is pressed on his statement: “We don’t need to be subsidizing energy in any form or fashion.” That would seem to mean that the Texas governor is against all the tax breaks for oil and gas. Is that really his position now?

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