In a recent Op-Ed, McCain criticizes Obama in his lead up to and handling of the crisis. He says Obama lacked resolve in Afghanistan and Iraq and allowed Bashar-al-Assad to cross his 'Red Line' without repercussions. He claims that Putin sees this lack of resolve as weakness to exploit.
McCain doesn't recommend military action other than NATO exercises, but he strongly insists on sanctions, removing Russia from the G8 and refusing Russian oligarchs places in the West to "park their ill-gotten proceeds."
It's a rare occasion to see how two leaders would deal with a crisis. Let's see what Obama does.