McCain and Obama tangle over Iraq pullout

By Andy Sullivan

TYLER, Texas (Reuters) - Republican John McCain and Democrat Barack Obama faced off on Wednesday in a possible prelude to a U.S. presidential election battle, tangling over whether Iraq would be prey for al Qaeda if U.S. troops are withdrawn.

Democrat Hillary Clinton, who needs big wins in Texas and Ohio next Tuesday to salvage her struggling candidacy, declared herself optimistic about her chances following her final debate with Obama on Tuesday night in Cleveland.

"What keeps me optimistic is the success I've had thus far and what I think the prospects are for Tuesday. People have just been really rallying to my candidacy," she said on her campaign plane before an event in Zanesville, Ohio.

She received a new blow, however, when U.S. Rep. John Lewis, a leader of the American civil rights movement, switched his support from Clinton to Obama for his party's presidential nomination.

"Something is happening in America," the Georgia Democrat said in a statement explaining his shift. "The people are pressing for a new day in American politics and I think they see Sen. Barack Obama as a symbol of that change."

Arizona Sen. McCain and Illinois Sen. Obama looked past Clinton and quarreled anew over the war in Iraq as it approaches its fifth anniversary in March.

At 71, McCain would be the oldest person elected to a first presidential term; Obama, at 46, would be one of the youngest.

The unpopular war is an important fault line in the campaign for the November presidential election, with Democrats advocating a quick U.S. troop withdrawal while McCain insists a pullout would amount to surrender and give Islamic extremists a victory.