Is there any evidence of that? I know that 12% of people who voted for Sanders in the primary ended up voting for Trump in 2016, but where’s the evidence that they were ever Democrats? It’s just as possible that they were Republican-leaning voters who were attracted to Sanders’ message, or trying to sabotage the Democratic primary. That’s a really good narrative for Clinton supporters to soothe their chagrin at the electoral college loss, but as that article points out, that number is actually pretty par for the course in elections.