Donald Trump is heading to November like a certain zeppelin heading to New Jersey, in a darkening sky that crackles with electricity. He is fighting crosswinds and trying new tacks — hiring the head of Breitbart News to run his campaign, trying on a new emotion (regret) in a speech on Thursday night, promising to talk more this week about immigration, his prime subject. There’s still no telling what will happen when the gasbag reaches the mooring.

It could be that the polls are right, and Mr. Trump will go down in flames. But while that will solve an immediate problem, a larger one will remain. The message of hatred and paranoia that is inciting millions of voters will outlast the messenger. The toxic effects of Trumpism will have to be addressed.

The most obvious damage has already been done — to the debate over immigration, a subject that is America’s pride but that can also show the country at its worst. Mr. Trump’s solution is to build an unbuildable border wall and force 11 million people out of the country, while letting millions of “good ones” back in. Or maybe not — now he says he wants to bar immigrants from most of the world, except for a few who pass religious and ideological tests. “Extreme vetting,” he calls it, bringing the Alien and Sedition Acts and McCarthyism into the reality-TV age.

Yes, Mr. Trump speaks frontier gibberish. Outright nativism remains a fringe American phenomenon. But there is no shortage of mainstream politicians who have endorsed his message by endorsing the Republican nominee. Anyone hoping to build a serious solution to immigration after this election will have to confront the unworkable ideas and vicious emotions that Mr. Trump, with many enablers, has dragged into the open.