"Imagine those 19 hijackers [on Sept. 11] with other weapons and other plans — this time armed by Saddam Hussein."

The "what if" argument still has power. But there are signs a correction is setting in.

To a degree unimaginable before the Iraq war, critics are now forcefully pressing that latter case. Robert Keeley, ambassador to Greece under Reagan, William Crowe, a retired admiral who was a chairman of the Joint Chiefs of Staff under Reagan, and Stansfield Turner, another retired admiral and past director of the CIA, were part of a group of 27 high-ranking former officials called Diplomats and Military Commanders for Change who issued a statement last week charging that Bush's policies had left the nation dangerously isolated in the world.

What if, Kerry seems to be arguing, Bush's answers to the toughest "what if" questions have actually made America less secure?