They Know
Greg Theilman is the former director of the Office of Strategic Proliferation and Military Affairs for the State Department under Colin Powell. As you might surmise from his title, his office was directly responsible for evaluating intelligence regarding Iraq's WMD programs.

In this interview for 60 Minutes, Theilman says that he'd known for months prior to the invasion that there was no evidence to support the Bush administration's claims that Iraq proposed an imminent threat.

And he told Powell, who should have told the President.

Now, while this is just the latest example of White House lies by omission & exaggeration, I think it's part of a larger trend in our culture. (see above)