There's a temptation to accuse John McCain of playing politics on Iran. I think this gives John McCain too much credit. What McCain knows is that Democrats--especially Democrats like Obama--are always weak on defense. I don't think there's much more to it.
Watching McCain go after Obama over Iran, is like watching Vinny Testaverde repeatedly throw deep into double coverage. McCain isn't reading the defense. He isn't looking anybody off. He's staring his reciever down. It's all he knows.
He'd do well to remember that the last time he did this, Barry took it back for six. But I wouldn't count on that.