I was at those protests, but pretending that the Iraq war was a purely Republican partisan contrivance is historical revisionism.
Here's the voting record for the authorization for use of force in Iraq:
House: For: 296 (R:215, D:81), Against: 133 (R:6, D:126, I:1) [0]
Senate: For: 77 (R: 48, D:29) , Against: 23 (R:1 , D:21, I1) [1]
Yes, there was more opposition from members of the Democratic Party, but there's quite a lot of support there from Dems.
[0] https://clerk.house.gov/evs/2002/roll455.xml
[1] https://www.senate.gov/legislative/LIS/roll_call_votes/vote1...