AMES, Iowa (Reuters) - Democratic presidential contender Barack Obama (news, bio, voting record) drew a contrast with rival Hillary Rodham Clinton on the Iraq war on Sunday and said it was unclear how she planned to end the conflict. On the day after he formally launched his 2008 White House bid, Obama said on a campaign swing through Iowa that even before the war began it was possible to see the dangerous consequences of a U.S.-led invasion of Iraq. "Even at the time, it was possible to make judgments that this would not work out well," the Illinois senator told...