McCain's "cross in the dirt" story

Andrew Sullivan has a good post expressing skepticism about McCain's anecdote about a prisoner guard who loosened his ropes and explained this gesture of mercy by way of silently drawing a cross in the dirt. It seems that McCain had never mentioned this amazing incident until 1999, when he co-wrote his autobiography The Faith of My Fathers, and that the story bears a striking resemblance to one first told by "evangelical leader and former Watergate crook" Chuck Colson in a book published in 1983.

If I had to bet, I'd wager that the anecdote is false. That said, though, I think that it is an open question as to whether the falsehood was intentional or not. Memory is surprisingly malleable--counter-intuitively so--such that a memory can become fused with other memories or even stories about other people, with its details shifting over the many years and retellings. (In fact, this happened with an anecdote that Josh used to tell: what really happened is that, once upon a time, I contemplated doing something unmentionable involving a bar of soap to get back at someone for throwing a muffin at me mid-shower, but somehow over the years the story turned into that I actually did the unmentionable thing, which is false. It took me quite a while to convince Josh that his memory of the incident was completely fabricated.)

In any case, even if he did make it up, it's not the sort of thing I get very riled up about. However, the more McCain leans on this anecdote--making it the centerpiece of a campaign ad, using it to bolster is Christian bonafides, etc.--the more I want to see someone press him for an explanation of why he didn't mention it until 1999.