That was a weird statement. What other meaning could it have?
He'll probably weasel that he was talking about the hypothetical possibility of having won the 2004 election.
He was responding to a point that he should have gone to NH - and that indirectly would have helped him win the presidency. I'm pretty sure his response meant that he didn't need to go to NH or do other things to help him win - he should have just gone to the WH - implying that he was really elected President and robbed. I don't think he meant he should have gone to the WH and hit the Prez with a stone which is kind of a silly inference to make. He was just trying to be witty. I wouldn't read too much into it.
That was my impression too. But consider the source.
I read this as Kerry admitting he has no stones.
"What other meaning could it have?"
----my first thought on reading it was that he was implying (echoing Clinton) that were he in the WHite House instead of Bush, bin Laden would be dead long ago. I can't believe even a feckless idiot like Kerry would, even to showboat to an idiot Maher audience, talk about killing Bush himself.