I think Obama’s Achilles Heel is his thin skin. He hates it when anyone disagrees with him or calls him out on a lie. Every single time when he has been challenged is a concrete, articulate way, he has come across as a bitter tool.
Romney’s goal has to be to prevent Obama getting under his skin, while riling the president up until he makes a big gaffe like
“I’ll kick your ass!”
He apparently once said that to a Chicago lawmaker who had disagreed with him.