Whipping up adequate support for a full scale anti-insurgency war in Afghanistan, as proposed by General McChrystal, requires the skills of a demagogue. He must be willing to lie about the prospects of success and to demonize the enemy beyond even its real sins. Anything less and the patience of the public will soon run out.
I think Obama can be pushed far enough by politics and cynicism into committing to the war but not far enough to pull it off as a "wartime president". The most likely result is that like LBJ he will become too unpopular to run for a second term and will be succeeded by a Republican running on a pledge to bring the troops home.