Israeli Prime Minister Benjamin Netanyahu speaks during a news conference in Jerusalem on April 1. (Ronen Zvulun/Reuters)

BENJAMIN NETANYAHU has a long history of leveraging bigotry and divisiveness for electoral advantage. But as he has pursued his fifth term as Israeli prime minister against stiff competition, and faced the possibility of criminal prosecution if he falls short, Mr. Netanyahu has plumbed new depths of demagoguery. He declared that Israel is not a nation-state of all its citizens, “but only of the Jewish people.” He portrayed his principal opponent, former army chief of staff Benny Gantz, as beholden to “the Arabs” who “want to destroy” Israel. He railed against police and prosecutors he says have subjected him to a “witch hunt.”

Though he enters Tuesday’s vote as a slight favorite to form the next government, Mr. Netanyahu remains worried that his voters will stay home. So in a television interview on Saturday, he offered a new and sensational promise: In a new term, he said, he would “move on to the next stage” and “apply sovereignty” to all Jewish settlements in the occupied West Bank. That would rupture Israel’s long-standing commitment not to change the status of the territory except through negotiations with the Palestinians; torpedo the peace plan the Trump administration is hoping to unveil after the election; and place Israel sharply at odds with all those who still favor Palestinian statehood.

Some Israeli commentators dismissed the declaration as election-eve bluster, pointing out that Mr. Netanyahu had blocked annexation legislation by members of his own coalition as recently as last year. Yet the possibility that the veteran prime minister will act on his pledge if he is reelected appears very real. To remain in office, he most likely will have to form a coalition encompassing far-right parties, including one his own Likud movement shunned as racist until this campaign.

It is widely believed that one of Mr. Netanyahu’s top priorities would be the passage of a law that would block his looming indictment on an array of criminal charges, including bribery. Israeli analysts point out that his right-wing allies would almost certainly demand, as the price of their support for such an unsavory measure, that he follow through on his annexation promise.

Then there is the Trump factor. Until 2017, strong pressure from a succession of U.S. presidents, both Democratic and Republican, deterred Israeli leaders from annexation of Palestinian lands. But President Trump has granted Israel a string of major concessions — most recently, recognition of its annexation of the Golan Heights. Mr. Netanyahu and his allies have taken that as a sign that Mr. Trump could also be induced to recognize or at least accept a partial annexation of the West Bank.

The State Department offered no comment in response to Mr. Netanyahu’s statement. That might be taken as avoiding intervention in the election. But Mr. Trump has already done an enormous amount to favor the Israeli incumbent. If the result is a new Netanyahu government that destroys the last hopes of an Israeli-Palestinian settlement, Mr. Trump will bear much of the responsibility.