Imagining the moment of John McCain's epiphany

What persuaded John McCain to see that the hateful course his campaign has been pursuing for the past 10 days is counterproductive?

I'd like to think part of it was common decency. Another part may have been a wish to inoculate himself from blame if, God forbid, some horrible act should be carried out by a whipped-up partisan.

Other factors might include the growing number of Republican politicians and talkers who have come out to say he's going down the wrong road, and the polls that show his attempts to soil Obama's character can be brushed right off like so much clean sand.

If McCain is smart, and I do think he's at least shrewd, the tipping point may have been his realization of the truth in this statement by John Weaver, a former adviser who was sent away in last summer's campaign staff housecleaning: