Last week, a Wall Street Journal/NBC News poll found a third of Bernie Sanders’s supporters saying they wouldn’t vote for Hillary Clinton in November if she’s the Democratic nominee, and nearly 60,000 people have signed the “Bernie or Bust” pledge. This is causing plenty of hand-wringing, with one Salon writer warning that “Bernie supporters could blow this election,” and a Huffington Post columnist calling it “the Democrats’ worst nightmare.”
But if history is any guide, a mass defection of Democrats and Dem-leaning independents is the last thing anyone should worry about. We’ve seen this before and we know how it will play out.
Ironically, in 2008 it was Clinton supporters vowing to stay home—or vote for John McCain—if Obama became the nominee. At the time, that same HuffPo columnist warned that “balkanized Democrats could give the White House to John McCain.” That May, primary exit polls found less than half of Hillary Clinton’s supporters in Indiana and North Carolina saying they’d consider voting for Obama in the general election. Even in early July, after Obama had secured the nomination, only 54 percent of Clinton backers said they planned to vote for him.
Those self-described “PUMAs”—“party unity my ass”—may have stayed home by the dozens that November, but at the end of the day nine out of 10 Democrats supported Obama in an election that featured the highest turnout in 40 years. A similar dynamic played out with Howard Dean supporters in 2004.
In the summer of 2008, George Washington University political scientist John Sides took to the pages of the Los Angeles Times to tell everyone to calm down. “Despite ugly battles and policy differences that sometimes seem intractable, the reality is that presidential campaigns tend to unify each party behind its nominee,” he wrote.
Political scientists call this phenomenon the “reinforcement effect.” It was described in 1940 in the first major study of a presidential campaign. The study’s authors…noted that voters tended to “join the fold to which they belong,” with Democrats gravitating to Franklin D. Roosevelt and Republicans to Wendell Willkie. These voters were not blindly following whichever shepherds their parties nominated, the study concluded. Rather, their partisan loyalties reflected their underlying values, and the parties’ nominees solidified their support by emphasizing these same values as the campaign unfolded.