I think the OP has a point. I think an increasing number--an increasing majority--of Americans realize that the Iraq War was a mistake. If the GOP nominee insists on defending the war, he/she will hurt their chances to win.
But the Democrats have an Iraq problem too because Obama failed to keep a residual force in Iraq and thereby invited the disaster that we see unfolding. Wrong or not, the Iraq invasion did establish a democratic government, and if Iraq descends into a Jihadist and Iranian puppet state, Democrats will be on the hot seat for Obama's failure to leave a residual force.
Obama "couldn't" keep a residual force in the country. The Iraqi government would not grant diplomatic immunity to the US military personnel, so the US was forced to leave, otherwise the soliders could be trialled in Iraqi courts and put to death completely outside the US's control.
It was the Iraqi Government that ended the war in the end, not Obama or even Bush even though Bush signed the treaty to in 2008.
There is no mentions of any residual force to remain in Iraq in the bill signed by Bush in 2008 to end the war, btw.