(CNN) -- Mitt Romney had another debate Saturday night in which he didn't make many mistakes, was smooth, knowledgeable, even presidential. It was his worst performance yet. The game has changed, and someone forgot to tell him. He is behind in national polls, and this time it's serious: His main rival, Newt Gingrich, is polling well not just in Iowa, but also across the country. Saturday night's debate was on a major network, with a wide audience, in the first state in the nation to hold a caucus -- and there is only one more debate before that voting. The conclusion is inescapable. Romney blew it.
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Todd Graham: Mitt Romney had a bad debate in Iowa, didn't seem to know he's trailing in polls
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He says Romney needed new strategy, but he blew chances to go after front-runner Gingrich
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When other candidates attacked him and Gingrich, Romney failed to differentiate himself
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Graham: Gingrich acted ready to take on Obama; Romney acted as if he were trying not to lose
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For his part, Gingrich seemed to escape the other candidates' criticism, partly because it was split (some attacks were aimed at @placeholder), and because the discussion did not stay on one topic for long enough to make Gingrich defend his positions in depth.