Democrats and Republicans can agree on one thing coming out of their respective conventions: Almost no one cares about Covid anymore. Infections are running rampant after the Democratic confab in Chicago, with staffers on Vice President Kamala Harris’ campaign, reporters and other convention-goers all stricken — and in at least one case claiming the positive test was “worth it.” Cases also cropped up after the Republican National Convention in July. And yet the single most-animating...