From a NYT article about Kerry's floundering campaign:
At a recent meeting of senior staff members, Democrats said, Mr. Kerry's aides became entangled in a lengthy debate over what might seem to be a less than urgent issue: whether they should send a Democratic operative to Bush rallies dressed as Pinocchio, a chicken or a mule, to illustrate various lines of attacks Democrats want to use against Mr. Bush. (They say they want to portray him as a liar, a draft avoider and stubborn.)If a Democrat political operative were to do that, they'd probably be mostly ignored by everyone except the media.
But try to imagine a Republican operative doing something similar at this rally... they'd be torn to shreds.