From the Boston Globe blog ...

One of the most enduring taboos in American politics, the airing of graphic images from the September 11 attacks in a partisan context, died today. It was nearly seven years old.

The informal prohibition, which had been occasionally threatened by political ads in recent years, was pronounced dead at approximately 7:40 CST, when a video aired before delegates at the Republican National Convention included slow-motion footage of a plane striking the World Trade Center, the towers' subsequent collapse, and smoke emerging from the Pentagon.

The September 11 precedent was one of the few surviving campaign-season taboos. It is survived by direct comparisons of one's opponents to Hitler.