JOHNS: Behind the scenes, Kerry's aides were fighting the swift boat charges with unusual ferocity. They say they have evidence one of the top members of Swift Boat Veterans for Truth is an outright liar.

The co-author of the book "Unfit for Command," former swift boat commander John O'Neill said Kerry made up a story about being in Cambodia beyond the legal borders of the Vietnam War in 1968.

O'Neill said no one could cross the border by river and he claimed in an audio tape that his publicist played to CNN that he, himself, had never been to Cambodia either. But in 1971, O'Neill said precisely the opposite to then President Richard Nixon.

O'NEILL: I was in Cambodia, sir. I worked along the border on the water.

NIXON: In a swift boat?

O'NEILL: Yes, sir.

(END VIDEOTAPE)

JOHNS: Now, O'Neill may have an explanation for this but he has not returned CNN's calls. What does seem clear is that a top member of the swift boat group is now being held to the same standard of literal accuracy they've tried to impose on John Kerry -- Aaron.