Mitt Romney's big debt to Newt Gingrich Democrats in 2008 fretted that the long, bruising primary campaign would damage their party's eventual nominee. And in some ways it probably did. Some political professional believe President Obama's standing among blue-collar white voters in Pennsylvania never recovered from the attacks Hillary Clinton made on him there. But the campaign also turned Obama into a more effective candidate, as (I think) Obama himself would later admit. With each debate and each exchange of negative advertisements, Obama became more focused, more aggressive, and more capable of holding his own. Those new skills served him well in the fall, when he debated the more experienced John McCain. Republicans this year have expressed similar worries, as the campaign of presumptive front-runner Mitt Romney has stumbled, thanks mostly to attacks from Newt Gingrich and his supporters. But Thursday night's debate makes me wonder whether the same dynamic is at play, because Romney was sharper than I've seen him a while. Romney has always been a quick thinker. But he's struggled to parry attacks from Gingrich, particularly when the subject of those attacks has been Romney's wealth and record in business. When Gingrich accused Romney of being "anti-immigrant," Romney turned to him directly and said he was offended by the label, since his own grandparents came from Mexico. When Gingrich said Romney owned shares of Fannie and Freddie Mac, Romney pointed out that Gingrich had investments in those companies, too. When Gingrich said Romney's wealth should be an issue, Romney said he was proud of his success as a financier - and that it was the kind of success conservatives should celebrate. Florida Republican debate: Winners & losers Gingrich, Romney at each other's throats over immigration Gingrich, Romney agree to blame the Palestinians, Obama for lack of progress in the peace process Gingrich hints at making Marco Rubio VP Gingrich, Romney hit each other over involvement in Fannie Mae and Freddie Mac Romney tells Gingrich: I'd fire you for your moon proposal I can't be sure how effective those answers were. And my hope is that somebody digs deeper into some of his statements like when he claimed not to know about an ad that his own campaign was running. My theory: He knew about it, but, having commented previously on an advertisement by his technically independent Super-PAC, he thought he had to profess ignorance this time. But my gut tells me that Romney, who has a new debate coach, impressed Republican voters much more than he has in the past. Part of the problem for Gingrich, I suspect, is that he's run into an ideological obstacle. Romney's issue positions - on immigration, the housing crisis, and his economic beliefs - are easy to attack. But are easy to attack from the left. You have to say that Romney is too rigid on immigration, too inattentive to people struggling with their mortgages, too wedded to conservative philosophy about the economy. And Gingrich can't say those things in a Republican primary. Early on, Gingrich could avoid that problem by focusing on Romney's hypocrisy or, in some cases, on the fact that Romney seems out of touch with average Americans. He couldn't do that on Thursday. Of course, Obama won't have the same problem. He can make those arguments and, most likely, they'll find a receptive audience not just among Democrats but plenty of uncommitted voters, as well. And if they seem less novel, because Gingrich has started this argument already, they'll also seem more accurate. In that sense, the primaries have not been so helpful to Romney. And there's still at least one question Romney hasn't figured out how to answer: How was the health care plan he signed as governor of Massachusetts different than the one Obama signed as president? Santorum made that point on Thursday and, for a change, he refused to let it go. All along, Romney's response has been to defend what he did in Massachusetts - an argument he makes very, very well - and then to suggest it was an wrong for Obama to impose it on other states. I can't imagine that's persuasive to conservative voters, who consider the law an abomination, full stop, although I'm not sure it will keep Romney from winning the Republican nomination. By the way, that exchange over health care came in response to a question I've been waiting to hear for a long time: We know the candidates want to repeal Obamacare, but what are they planning to do instead? The answer was important - and worth a more lengthy response. But that's a subject for another day. The opinions expressed in this column are solely those of the author.