“Only 53 percent of Sanders voters say they will certainly support whoever is the Democratic nominee. This is no idle threat. In 2016, in Pennsylvania, 117,000 Sanders primary voters went for Trump in the general, and Trump won the state by 44,292 ballots. In Michigan, 48,000 Sanders voters went for Trump, and Trump won the state by 10,704. In Wisconsin, 51,300 Sanders voters went for Trump, and Trump won the state by 22,748. In short, Sanders voters helped elect Trump.”
http://nytimes.com/2020/02/06/opinion/trump-democrats-2020.html