Rich's column suggests that McCain-Palin's rhetoric is risking the assasination of Sen. Obama. His evidence:

"raucous and insistent cries of 'Treason!'" links to "a crowd member [that is, one crowd member] screamed "treason!" during an event on Tuesday after Sarah Palin accused Barack Obama of criticizing U.S. troops.

"raucous and insistent cries of ... 'terrorist' and 'kill him!'" links to a story in which one reporter claimed that one crowd member allegedly shouted kill him, likely referring to, if anyone, Bill Ayers, and also mentioning that "a male member of the crowd in Jacksonville, Florida, yelled 'treason!'"

"the uninhibited slinging of racial epithets,'" links to a story in which one member of one crowd slung a racial epithet at a cameraman.

So, of the hundreds of thousands of people who have attended McCain-Palin rallies, we have a grand total of four [update: Rich has one more equally tenuous link, so make that five] whose conduct is said to taint the campaigns. Heck, I can find four similarly unpleasant comments on a typical DailyKos thread.