More than a dozen Washington Post columnists signed on to a scathing response to their own leadership’s decision not to endorse a presidential candidate, calling the choice a “terrible mistake” and an “abandonment” of its “fundamental editorial convictions.” For the first time in more than three decades, the Post, which is owned by billionaire Amazon founder Jeff Bezos, said it would not endorse a candidate in the presidential race. The move led to widespread backlash — and even a flurry of subscription cancelations from big names — as critics pointed to the newspaper’s slogan: “Democracy dies…