By Mark Willen, Senior Political Editor April 11, 2008 Polls show that by overwhelming margins voters want the U.S. out of Iraq as soon as possible. So how is it possible that the war could help propel John McCain to victory? Listening to the testimony of Gen. David Petraeus this week, it was hard to find cause for optimism. "We haven't turned any corner," he said. "We haven't seen any lights at the end of the tunnel." Democrats Hillary Clinton and Barack Obama wanted to know where we are headed, pressing Petraeus to describe what conditions will allow the U.S. to depart and looking for a definition of success. They didn't get either. McCain was more focused on the effects of defeat, concerned that a departure anytime soon will reverse the gains he believes have been made as a result of the surge and concerned about the chaos and shame that a defeat will bring for the U.S. McCain spoke of persevering until the U.S. is victorious and successful, without explaining how those ends might be achieved. Still, that's an appealing approach, one that can work for McCain politically no matter what the polls say because it taps into the hope that all Americans want to feel, even when their judgment suggests it may be an unreal hope. And while polls show most Americans think that the war was a mistake, they also show that a majority now believe the war is going better than before the surge. If voters continue to believe that, McCain's optimism and determination -- which strike a chord with Americans, who hate giving up hope and accepting failure -- could prove a big advantage.