Not surprisingly, the right wing response to Scott McClellan's book has prominently featured the "everybody thought Saddam had WMD" argument. I.e., it is not Bush's fault that we are fighting a needless war; he got bad intelligence. While it is true that it was widely believed that Saddam had chemical weapons, this argument purposefully obfuscates all the ways in which the Bush administration misused the intelligence by mixing together questions that should be considered separately.
Let's consider the questions about intelligence individually.
Did everyone think that Saddam had chemical and biological weapons?
Yes. More of Less.
Did everyone think that Saddam was stockpiling such weapons for future operations?
No. Many people thought Saddam only had residual capability from the Iran-Iraq war.
Did everyone think that Saddam was trying to rebuild his nuclear weapons program?
No. Hardly anyone thought that he was trying to do so.
Did everyone think that Saddam was buying aluminum tubes for centrifuges.
No. Most experts thought not.
Did everyone think that Saddam was trying to obtain uranium from Niger?
No. Almost everyone knew this was bogus.
Did everyone think that Saddam was likely to use his chemical weapons if he was not attacked?
Did everyone think that Saddam was connected with Al Queda?
Did everyone think that Saddam would to provide weapons to terrorists?