Democrats really, really want to defeat President Trump. That’s the message from Joe Biden’s primary victories on Tuesday as he further deflated the hopes of Bernie Sanders and his revolution.

If Democrats had buyer's remorse after Mr. Biden’s stunning comeback on Super Tuesday last week, they didn’t show it as he rolled to easy wins in Mississippi, Missouri and Michigan. The victory was especially impressive in Michigan, where Mr. Sanders won narrowly in 2016 but Mr. Biden led by 14 percentage points by our deadline. Washington state was too close to call.

The Vermont Senator campaigned heavily in the Wolverine State, especially in college towns full of social-justice warriors and gentry liberals. Mr. Sanders won voters under age 29 by about 82% to 15%, according to the exit polls, but they were only about 15% of the electorate. Voters older than age 65 made up about a quarter of the Democrats who cast ballots, and Mr. Biden won them 73% to 23%.

Mr. Sanders tried to turn Democrats against Mr. Biden in Michigan by running against Nafta, and charging that the former Vice President would slash Social Security and Medicare. But Democrats don’t believe the latter, and trade has gained support among Democrats as Mr. Trump has co-opted the protectionist agenda.

The mass voter mobilization of the proletariat that Mr. Sanders promises simply hasn’t materialized. As that fact becomes clearer to Democrats who want to win in November, Bernie’s chances of a comeback diminish even more.