From Bernie himself, via a recent campaign email:
I want to say a few things about Donald Trump and specifically about his comments tonight that we should ban all Muslims from coming to the United States, even American Muslims returning home from overseas.
It’s fun for the political media to treat Donald Trump like he’s the lead character in a soap opera or the star player on a baseball team. But the truth is his language is dangerous, especially as it empowers his supporters to act out against Muslims, Latinos, and African-Americans.
Poll after poll shows that I am the candidate best suited to take on Donald Trump and every other Republican running for president.
With multiple opinion polls showing Bernie being the most electable Democratic presidential candidate in hypothetical matchups against Trump, it’s clear that we need to do everything possible to help Bernie to win the Democratic nomination. One thing you can do is vote for Bernie Sanders in the Democracy for America (DfA) online poll. Should Bernie get at least two-thirds of the vote in the online poll, DfA will endorse Bernie.