Joe Biden sure knows how to pick ’em. The Democratic nominee had the opportunity to name a competent female running mate, one who would excite his base and reassure undecided voters. He instead chose California Sen. Kamala Harris, the definition of political mediocrity. Don’t take Donald Trump’s word for it. Take the left’s—at least a few months ago, when it had no stake in creating a legend. The media and Democrats this week can’t roll out enough praise for the veep pick: She’s brilliant, savvy, seasoned, vetted, smooth, forceful, appealing, authentic, powerful, a fighter. This is the same woman the...