The Obama 16-month withdrawal position continues to bounce between an ideological (anti-war) and conditional (national security) one.  He wants to have it both ways, which we find confounding but he finds expedient.  In my opinioon, McCain has not come closer to Obama's position.  McCain's position, like Bush's, has always been a conditional one, based on circumstances/conditions not ideology.  If leaving Iraq, in whole or part, in 16 months can be done without harming our national security (broadly defined), then neither McCain nor Bush would hold out for more time.  Why would they?