President Trump, bless him, has once again achieved the impossible: He has unified the Democrats. The fractious opposition party had been holding one of its regular Festivals of Gratuitous Self-Injury over the past few weeks on the matter of race. Sen. Kamala Harris (Calif.) and other Democratic presidential candidates had attacked the “hurtful” actions of front-runner Joe Biden from decades ago in opposing busing and in working with segregationist senators.