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.
In this case, Clyburn is the most influential Democrat in the state. He is the no. 3 ranking Democrat in the House and the most powerful African American in a state where over 60 percent of the Democratic primary electorate is Black.
If you follow @fivethirtyeight, and you should, famed political prognosticator @natesilver538 ranks Clyburn’s endorsement as equivalent in influence to Barack Obama’s endorsement. You read that right.
In my @uscpress book on the South Carolina primary with @gibbsknotts, we have a chapter on “what it takes to win” the #firstinthesouth primary. Our results confirm the above: endorsements matter here. Quantifying the value of Clyburn’s endorsement is difficult, however.
In the book we don’t test the effect of any one person’s endorsement given the obvious sample size issues. For example, Clyburn hasn’t always endorsed—he refused to do so in 2008. Rather, we test the effect of their volume and quality in the aggregate.
With that big caveat, we find candidates that secure a large volume of high-quality endorsements perform 4.7% better in the South Carolina primary (controlling for other factors in race). I think this is the most conservative estimate of what Clyburn’s endorsement is worth.
Consider Nikki Haley’s endorsement of Marco Rubio in 2016. Prior to her endorsement, Rubio seemed poised to finish 3rd or even 4th, yet he vaulted into 2nd ahead of Ted Cruz. It was a key moment in 2016 and helped keep Rubio in the race for another three weeks.
With Clyburn’s endorsement, and a strong debate performance yesterday, it would be surprising if Biden doesn’t win the Democratic primary on Saturday. He has led in every poll dating back to last year and should get a poll bounce in the coming days.
Looking beyond South Carolina, Clyburn’s endorsement reveals Biden’s path to victory. Influential Democrats in the coming states need to rally behind Biden and use their considerable clout. Obvious problem: there may not be a Jim Clyburn in every state.
