Now that a WMD can be a kitchen pressure-cooker (Tsarnaev brothers), the WMD argument has fallen flat.
That WMD being a pressure cooker came from the lowering of the WMD argument while Clinton was President.
He needed excuses to go into Somalia and Iraq (the Senate gave him the authority but he never executed). WMD originally meant only Nuclear weapons, but was expanded to biological and chemical in the 1990’s, especially after Oklahoma. Once they started lowering the bar, they lowered it all the way to the floor.
The Wiki page for weapons of mass destruction is surprisingly accurate in covering this adaptation.