When President-elect Joe Biden named his longtime associate Ron Klain as his White House chief of staff, it was widely interpreted as a sign that the new president’s administration would represent the same mainstream and moderate Democratic Party establishment that both of them epitomized. That was, after all, why Biden had won the presidency after a lifetime of effort aimed at that one goal. SENATE DEMOCRATS FACE A BRUTAL MAP But with the announcement of Klain’s resignation as chief of staff after two years of hard service, one thing is clear. Expectations that he would be the “prime minister” who would shepherd the administration on a reasonable and moderate path were mistaken. Though Klain ran a fairly tight ship in the West Wing with little of the infighting and chronic factional leaking that characterized the...