I thought Iraq didn't have any WMD

With a record like that you'd have to assume he still had them and would use them.

You can assume nothing, they presented the "evidence" and it was laughed at, several of the nations doing the laughing had already examined the evidence and passed it on to America with a note saying it was bollox.
Didn't your secretary of state describe presenting that pile of tripe as the lowest point in his career.

As for who (supposedly) lied,you can add Clinton,Gore and most of the Democratic leadership as well.

It isn't a party thing, some people at the time lied, some people at the time swallowed rubbish and some people just went along for the ride because the truth of the claims didn't matter to them at all.
However, for people to still try and peddle the rubbish that has long been proven as absolute crap is absolutely ridiculous and simply demonstrates that they cannot learn from their mistakes or accept the reality of them.