I don't think that the general public will blame Trump as the cause of the riots, but now that things have gotten so out of control that the MSM is reporting, the public may ask, why in the heck hasn't Trump done something under his watch? I see that as a possibility. If he is allowing things to continue for strictly political purposes, then absolutely shame on him. However ....
People have three choices - Trump, Biden, stay home.
With cities burning and lockdowns continuing I do not believe people will stay home. This election of ALL elections.
I do not see people voting for Biden because they see Trump taking political advantage of the riots. If they are pro riots it doesn't matter what Trump does. If they are anti riots, since the rioters have made it clear they hate Trump, then the choice is clear. This applies to the most dense voters.
More astute voters realize why Trump has done what he has, that he has made it clear he stands ready to assist if invited, as the Constitution requires. And they are aware of the game the left is playing here, if Trump plays the wrong hand he loses and so we will all lose.