AUSTIN: Barack Obama escaped unscathed from a key debate which Democratic foe Hillary Clinton hoped to use to slow his surging White House quest, 12 days before their next electoral showdown. On another day of high drama in the relentless 2008 election, presumptive Republican nominee John McCain meanwhile was forced to deny he had an extra-marital affair after a report linked him to a female lobbyist.

Senator Clinton needed a game-changing moment at Thursday night’s debate at the University of Texas, as new polls showed her rival slashing her leads in her must-win fortress states of Texas and Ohio, which vote on March 4.

Obama meanwhile avoided serious gaffes, fought back against her claims that some of his soaring oratory was plagiarised, and suggested her vote to authorise war in Iraq sparked questions about her leadership skills. “If your candidacy is going to be about words, then they should be your own words. That’s, I think, a very simple proposition,” Clinton said, drawing cheers and some jeers from the audience at the University of Texas.

“Lifting whole passages from someone else’s speeches is not change you can believe in, it’s change you can Xerox,” the New York senator said, ripping off her rival’s campaign slogan.

But Obama rejected accusations that he had stolen language from Massachusetts governor Deval Patrick as “silly season” politics and in a cheeky quip defended his speeches: “I’ve got to admit, some of them are pretty good.” In her strongest moments, Clinton scored points on her signature issue of healthcare, and at the end of the encounter gave an emotion-tinged answer on her greatest personal challenges.