It never came up in the GOP primaries. The mainstream media won’t dare mention it. Even John McCain’s most liberal opponents won’t go there. But leave it to equal opportunity offenders, brothers Evan and Gregg Spiridellis and their animation team at JibJab, to introduce into the 2008 presidential campaign the allegations that John McCain cooperated with the enemy when he was a prisoner of war in Vietnam.

Not that most people will notice it. The reference comes about one minute into the group’s latest campaign video, “Time for Some Campaignin’,” when the McCain character sings that he “spent years in a rat hole in North Vietnam” over animated graphics showing him swinging in a bird cage — a reference to the fact that McCain’s accusers refer to him as “Songbird.”

A charge as heinous as collaborating with the enemy may sound like liberal revenge for the Swiftboating of John Kerry by Republicans in 2004, but the allegations against McCain come from conservatives, notably including former Rep. Bob Dornan of California and former Sen. Bob Smith of New Hampshire, both of whom are Republicans.