With reference to weapons of mass destruction: It is a fact that Iraq under Saddam had made and used WMD in the past - definitively against Iran and almost certainly against Kurds internally. It is a fact that UN inspectors did find clear evidence of the manufacture of and, in some cases, the actual weapons, after the 1991 Gulf War.
The more recent evidence is less definite, but at the least strongly indicated that Saddam was working hard to maintain the capacity to manufacture chemical WMD, and to develop working biological and nuclear WMD. It appears clear that he was certainly flouting the non-WMD restrictions imposed by the UN (long-range missles, etc.).
In my opinion, based on the evidence so far, Saddam was doing his best to convince the world that he actually had WMD whether he did or not. Whether this was simple egotistical posturing, a calculated strategy to discourage US intervention, or a ploy to increase his popularity with potential allies, I hesitate to guess. I don’t much like the man, but I think, based on the evidence available to them at the time, that Bush and his advisors had to assume that either Saddam had WMD or would soon have them, and didn’t want to wait until they had incontrovertable proof when he actually used them on someone, possibly the US. I would see this as a reasonable worst-case interpretation of the evidence rather than a lie. (Whether this justified an invasion of Iraq is another issue.)