MANCHESTER, N.H. — Mitt Romney offered a tepid defense of the Massachusetts health care law, suggesting to an audience last night at the Granite State’s first forum of the 2012 presidential campaign that he would sign it again if given the chance. “I went to work to try and solve a problem,’’ Romney said. “It may not be perfect — by the way, it is not perfect.’’ The statement was in response to a question asked of the former Massachusetts governor after he delivered a short address that was equal parts patriotic fervor and attacks on President Obama’s economic policies....