Top Democrats on Monday reacted to the 4,000th U.S. death in Iraq by calling for a change in policy.Democratic presidential frontrunner Sen. Barack Obama (Ill.) called the event a “grim milestone” and advocated a new course on Iraq. “It is past time to end this war that should never have been waged by bringing our troops home, and finally pushing Iraq's leaders to take responsibility for their future,” Obama stated.His rival for the nomination, Sen. Hillary Rodham Clinton (N.Y.), said at the onset of a speech on the economy that the news of the 4,000th U.S. death in Iraq is...