Wars often spur times of immense national unity — moments in which partisan politics dissipate and dissent is muted. This effect is famously temporary, and with respect to the Iraq war, it is clear that attitudes on whether it was a mistake break heavily along partisan lines, despite nearly unanimous initial support.
Not surprisingly, given that the war was begun in the administration of a Republican, former President George W. Bush, 66% of respondents who identify as or lean Republican say the U.S. did not make a mistake in sending troops to fight in Iraq, while 30% express the contrary view. In contrast, 73% of Democratic leaners or identifiers see the military campaign as a mistake. Twenty-two percent in that group say it was not a mistake.