Heather Cox Richardson, a center-left historian with the biggest following out of any individual on Substack, spread an appalling lie about Charlie Kirk’s assassin in a post published Sunday. Richardson has over 2.6 million subscribers to her Substack, a newsletter presumably read by scores of center-left, ‘normie’ liberals. She is a history professor at Boston College, has interviewed former President Joe Biden, and is planning to interview with The Bulwark. By no means is she a fringe figure, nor is she, at least on the surface, a radical; if anything, she is someone who would be welcomed on a show...