McCain has best debate but Obama unscathed

WASHINGTON (Reuters) - They saved the best for last.

Republican presidential nominee John McCain, his back against the wall, turned in his best debate performance on Tuesday in Hempstead, New York.

But Democrat Barack Obama was not knocked off his pedestal and emerged in a seemingly strong position, riding a lead in national opinion polls and Election Day less than three weeks away on November 4.

There were no game-changing moments that might have reshaped the nature of a race that is trending in Obama's favor.

"I didn't think Obama was as comfortable this time as he was in the other two debates, but I didn't really hear any gaffe, any major mistake," said Larry Sabato, a political science professor at the University of Virginia.

As a consequence, Sabato said, "He might even be judged the winner."

McCain got off the line of the night in rejecting Obama's argument that the Arizona senator is a clone of unpopular President George W. Bush.

"Sen. Obama, I am not President Bush. If you wanted to run against President Bush, you should have run four years ago," he said.

And in the last of the three debates McCain repeatedly raised the issue of whether Illinois Sen. Obama can be trusted, breaking his silence at these debates on Obama's ties to 1960s radical William Ayers, a founding member of the anti-Vietnam War Weather Underground group that bombed the Pentagon and the U.S. Capitol in the early 1970s.

"That was McCain's best debate," said Republican strategist Scott Reed. "He had Obama on the defense most of the evening and he closed with trust. Trust and judgment are what this thing is going to be all about."

DOUBLE-EDGED TACTIC

But McCain was also in a quandary. To shake up the race he had to go on the attack, but the tactic was a doubled-edged sword, because attacking can turn off some voters.

In fact a New York Times/CBS News poll this week reported many Americans thought a recent negative turn taken by McCain had done him more harm than good.

Bruce Merrill, professor of media and mass communications at Arizona State University, thought that McCain did well, though not enough.

"I really think that his negativism, the attack mode was one that does not play well with women and independents," Merrill said.

Body language played possibly a bigger role in this debate than in the others. Obama openly laughed at some of McCain's points. McCain at times looked peevish.

Obama's goal going into the last face-to-face confrontation with McCain was to avoid any major stumbles, and his supporters believed he succeeded.

"I think Obama knew he had more to lose in this one than McCain frankly," said Democratic strategist Liz Chadderdon.

The big winner of the debate may well have been "Joe the Plumber" -- Joe Wurzelbacher of Holland, Ohio, who Obama ran into on the campaign trail recently and drew headlines for telling him he wanted to "spread the wealth around," which to McCain means he wants to raise taxes.

Joe came up about two dozen times as both candidates argued their economic and health care policies would help the plumber.

(Additional reporting by Tim Gaynor; editing by David Wiessler)