Marc A. Thiessen WASHINGTON — For months, Democrats ignored or excused the chaos engulfing our cities. Sen. Kamala D. Harris, D-Calif., went so far as to raise bail money for those arrested during the riots in Minnesota. The looting and vandalism went completely unmentioned at the Democratic convention. In his acceptance speech, Joe Biden condemned the violence in Charlottesville three years ago, but not the violence that was taking place in Portland, Ore., that very week. Now, all of a sudden, Biden is finally speaking out. What changed? The polls.…