James Clyburn endorsed Joe Biden this morning. What follows is a brief thread on how much this matters and what my book on the South Carolina primary with @gibbsknotts says about endorsements. Short version: this is indeed a big deal. #sc2020 #scpol #clyburn #firstinthesouth First, some theory. Endorsements can have a big impact in nomination contests since voters can’t rely on party-id like in general elections. Endorsements fill the void giving voters a “cue” to mimic an informed decision. Of course, this hinges on reputation of the endorser.