From Fear & Loathing On The Campaign Trail ’72, by Hunter S. Thompson:
Make Them Deny It
…(I)n both the Ohio and Nebraska primaries, back to back, McGovern was confronted for the first time with the politics of the rabbit-punch and the groin shot, and in both states he found himself dangerously vulnerable to this kind of thing. Dirty politics confused him. He was not ready for it….
This is one of the oldest and most effective tricks in politics. Every hack in the business has used it in times of trouble, and it has even been elevated to the level of political mythology in a story about one of Lyndon Johnson’s early campaigns in Texas. The race was close and Johnson was getting worried. Finally he told his campaign manager to start a massive rumor campaign about his opponent’s life-long habit of enjoying carnal knowledge of his own barnyard sows.
“Christ, we can’t get a way calling him a pig-fucker,’ the campaign manager protested. “Nobody’s going to believe a thing like that.”
“I know,” Johnson replied. “But let’s make the sonofabitch deny it.”