http://www.nytimes.com/2008/04/17/us/politics/17debate.html?pagewanted=1&ei=5087&em&en=5b0ead7db2f73f5e&ex=1208577600PHILADELPHIA — Senator Barack Obama found himself consistently on the defensive as he and Senator Hillary Rodham Clinton met Wednesday night in a tense debate that left him parrying questions and criticism on issues including values, patriotism and his association with onetime radicals from the 1960s.
Accordingly, Mrs. Clinton did not let an opportunity pass as she repeatedly challenged Mr. Obama on his record and views — assisted, as it turned out, by vigorous questioning by the two moderators from ABC News, Charles Gibson and George Stephanopolous.
The result was arguably one of Mr. Obama’s weakest debate performances. He at times appeared annoyed as he sought to answer questions about his former pastor, his reluctance to wear an American flag pin on his lapel and his association in Chicago with former members of the Weather Underground, a radical group that carried out bombings in the 1960s that were intended to incite the overthrow of the government.
The political implications of his performance remained unclear. As Mrs. Clinton was again reminded by a poll Wednesday in The Washington Post, there are risks to going on the attack as she has over the past six weeks: She is viewed unfavorably by an increasingly large number of voters. Mrs. Clinton can afford nothing short of a strong victory in Pennsylvania’s primary on Tuesday as she looks for a rationale to proceed with her candidacy and stir doubts about Mr. Obama’s ability to appeal to white, blue-collar voters.
Mr. Obama said that he had misspoken and that he understood why voters would be offended by those remarks. But he accused Mrs. Clinton of seeking to parse his words for political gain in a way that he said accounted for widespread cynicism about politics.
While the tone remained civil on the surface, the displays of affection that both had engaged in during some of their previous encounters — back slaps and lingering handshakes — were replaced by shots of the two candidates staring tensely at each other or gazing into the darkened auditorium at The National Constitution Center.
There was a brief moment of lightness at the start when Mr. Gibson asked whether either would endorse a proposal by Mario M. Cuomo, the former governor of New York, to promise that whoever wins the nomination choose the other as his or her running mate, and that the loser would accept. “So I put the question to both of you: Why not?”
The lengthening silence from the two candidates was filled by the laughter of the crowd.
Those issues were raised in a tough round of questions posed by Mr. Stephanopoulos and Mr. Gibson, who in many ways presented a mirror image of earlier debates in which two NBC moderators, Tim Russert and Brian Williams, repeatedly pressed Mrs. Clinton with tough and provocative questions.