At each stop, Bush will be dealing with vexing challenges that aren't about to disappear because of a change in the Oval Office. Obama says he will end the war in Iraq, but his own advisors admit that any U.S. troop drawdown would depend on advice from ground commanders and would be unlikely to get the U.S. all the way out soon. McCain criticizes much of Bush's approach to Iraq, but says now that we're there, we have to stay and win. Both men will find the diplomatic and military options for changing Iran's nuclear ambitions and anti-Israel stance as limited and ineffectual as Bush does. And if the President has learned anything from his recent spurt of Arab-Israeli diplomacy, it's that the militant anti-Israel groups, Hamas and Hizballah, are permanent, and intransigent, obstacles to the peace process.