Romney response to McCain's wise-assed quip

I have been, and remain, lukewarm to Mitt Romney's presidential candidacy. His response to John McCain's response to his opposition (follow that?) of the immigration bill is sharp, though:

I guess it just shows that, even when he's wrong, he's amusing.

That one sentence is incredible. In it, Romney mute's McCain's comment about varmint guns. He also makes McCain look small for making the comment. Finally, he holds his ground respectably. One sentence does not a President make, but it was enough to make me at least consider Romney as potentially presidential. Still, Romney has a big weakness, and that is that he currently is as vulnerable to the flip-flop charge as John Kerry was in 2004.