Instead of championing the urgent Palestinian interest in any of those imperatives, Omar’s rhetoric has provoked a pointless debate over the motivations and national loyalty of Americans who support Israel.

This plays into the hands of Israeli Prime Minister Benjamin Netanyahu, who is facing the most serious political crisis of his career. That’s crucial because as long as he remains in power, the revival of meaningful negotiations with Palestinians will be impossible.

Mr. Netanyahu can now mobilize Israelis and American Jews by claiming that they are under attack by Democrats, pushing those constituencies toward himself and his Republican allies.

Worse, enmeshing Democrats in a divisive, embarrassing internal struggle is a huge gift to Trump because it deflects attention from the impact of his destructive policies. Voters appalled by Trump’s trafficking in anti-Semitism now have reason to wonder whether the alternative might be just as bad.