That might seem crazy at first glance- there's no issue they have more differences on. Senator Obama opposed us going to war in the first place. Ah, but going to war is no longer the question.
President Obama won't bring the troops home one day earlier than President McCain would. All the experts agree that if we leave before a viable government is in place, there will be civil war and a bloodbath. President Obama will be very risk-averse in Iraq; no way in hell is he going to have the legacy of the first black President be "the man who lost Iraq" and "the man who gave us the Middle-East killing fields".
President McCain won't leave the troops in Iraq one day longer than President Obama would. Put these reasons in whichever order you wish: McCain knows that if the troops don't start coming home soon, the nation will become ungovernable- he did live through the Vietnam years, you know. McCain knows the horrors of war personally- he's not going to leave his beloved men and women in uniform in harm's way longer than he has to.
If you've been watching the last six months, the candidates have been moving closer to each other despite their rhetoric. Obama is now talking about not leaving precipitously, and McCain is now mentioning timetables. Both of them will rely on the same State Department and Pentagon experts when in office. So hold their feet to the fire about counterterrorism, and how to balance that against our freedoms- but don't let yourself be swayed one way or the other by emotional rhetoric about the Iraq war.