After John McCain delivered the central question of his speech yesterday -- "Who is the real Barack Obama?" -- the first, and loudest, supporter seemed to yell:

"Terrorist!"

That's what John Aravosis and Marc Ambinder heard, and it does sound like it.

McCain seemed to pause, and didn't denounce the epithet. I'd argue that there's no way to arrive at a conclusive answer as to whether he heard it or not, short of asking him and getting a frank answer. McCain could have been pausing to admire the pith and artfulness of his smear, or to bask in the adulation it brought. And McCain is not responsible for what some whackjob yells at his rally.

That said, the moment is uncomfortably revealing: McCain is now dabbling in the tactics employed in the most viral smears of Obama, if not to the same degree. No honest observer would dispute that McCain's speech today was about sowing fears of Obama as a risky, unknown, and vaguely sinister "other," and this supporter, at least, read the subtext, intended or not, loud and clear. And when McCain delivered that line there was a gratified, even visceral roar from McCain supporters, as if this attack -- fear the alien in our midst! -- was the gloves-off moment they'd been waiting for.

(Things got just as ugly at a Palin rally yesterday.  HuffPo has more.)