From today's Washington Sketch dispatch from a McCain/Palin rally in Pennsylvania:

A Washington Post columnist created two hand-lettered signs -- one saying "MAINSTREAM MEDIA" and the other, "I NEED A HUG" -- then carried them among the McCain supporters. McCain, and particularly Palin, have railed in recent days about the failings of the mainstream media, and Platt picked up the theme Wednesday, telling the crowd about "vicious attacks from the media."

The result was reassuring. Most of the McCain supporters enjoyed the sight, and several of them offered hugs or handshakes. Some others used the opportunity to give polite voice to their displeasure with the media. Only a minority in the crowd turned ugly. "Put your hands around me, you'll spit your teeth out," said one gentleman. "Barack Osama -- he'll give you a hug," said another.

UPDATE: Says one tipster:

I think Milbank is implying that HE is the Washington Post columnist and that HE was the one that walked around w/ the signs. He's done this before while on assignment, trying to gin up reactions.

And now the video proof...it was Milbank: