There he goes again.

With Republicans struggling to keep their grip on Congress, President Trump is dialing up the demagogy. At campaign rallies and on social media, he’s spewing dark warnings about a Democratic mob clamoring to usher in an era of open borders, rampant crime, social chaos and economic radicalism.

As is so often the case, Mr. Trump is not letting reality interfere with his performance. At a rally in Nevada this weekend, the president told the crowd that Californians were rioting to “get out of their sanctuary cities.” (They aren’t.) He also suggested that Democrats will soon be looking to hand out free luxury cars to illegal immigrants. (They won’t.) “Give ’em a driver’s license. Next thing you know, they’ll want to buy ’em a car,” he riffed. “Then they’ll say the car’s not good enough, we want — how about a Rolls-Royce?”

Mr. Trump’s Twitter feed has been electrifying as well, full of statements intended to thrill his fans — and, better still, bait his opponents into a partisan rage. In recent days, he has dubbed Stormy Daniels “Horseface,” escalated his taunting of Senator Elizabeth Warren as “Pocahontas” and grumbled about the fact that Bruce Ohr, one of Mr. Trump’s nemeses in the “rigged” Russian “witch hunt,” is still employed by the Department of Justice. He has asserted that the Democratic nominee for governor in Florida, Andrew Gillum, is looking to turn the state into “the next Venezuela.” He has threatened to dispatch troops to shut down the southern border and renewed his vow to cut off the “massive foreign aid” sent to El Salvador, Guatemala and Honduras for those nations’ failure to stop their people from flocking to the United States.

In particular, the caravan of Honduran migrants making its way north has emerged as a focus of his fantasies. Mr. Trump has repeatedly implied that Democrats are paying Honduran youth to join the caravan. On Monday, he claimed, based on nothing, that the caravan is awash in “criminals and unknown Middle Easterners.”