Donald Trump is calling for volunteers to watch the polls in November, and he is making no bones about why.

“Help me stop Crooked Hillary from rigging this election!” says the application form on his campaign website.

There are so many lies and delusions flowing daily from the Trump campaign that it’s easy to miss the times when the Republican nominee is being not just ludicrous, but dangerous. This is one.

Mr. Trump has seized on the charge that Hillary Clinton plans to win by cheating. He has said it before, but he keeps on saying it. This looks like pre-emptive face-saving, of course — getting an excuse ready if he loses badly. But it’s worse than that.