Congratulations are in order for Benjamin Netanyahu, who, in an astounding reversal of fortune, is likely to return as Israel’s prime minister for an unprecedented third time. The latest exit polls from the general election Tuesday — the fifth in four years — show that the leader of the Likud Party is in a position to extend a span in power that is already the longest in Israel’s history. It would be a remarkable show of political stamina and character.

Not that it is going to be easy. With something like 80 percent of the vote counted, it looks like a decisive victory for a coalition pledged to support Mr. Netanyahu. Yet members of such a coalition include some of Israel’s most far-right politicians. If Mr. Netanyahu seeks a coalition by relying solely on such parties, the country’s polarization could become wider and more bitter than it has been, which is saying something. 

The key figure in that drama is the right-wing leader Itamar Ben Gvir. He is a disciple of the martyred radical rabbi Meir Kahane. Mr. Netanyahu did his utmost to pull Mr. Ben Gvir out of the political fringe and into the main fold. In a repudiation of the current centrist government of Prime Minister Lapid, Mr. Ben Gvir’s party, Otzma Yehudit, which means Jewish Strength, emerged as what will be the third-largest party in the next Knesset.

This gives Mr. Ben Gvir leverage in negotiations over the new government. He’s said that he would seek to be minister of internal security, which would place him atop the police force and other bodies charged with law enforcement and fighting terrorism. Arab citizens of Israel will fear the prospect. What they see in Mr. Ben Gvir is a man who once worshipped Baruch Goldstein, a physician who in 1994 massacred 29 Muslim worshippers at Hebron. 

Mr. Ben Gvir has been making an effort to rebrand himself and drop his past, which includes a conviction for incitement to racism, yet nevertheless maintains policy prescriptions that put him far to the right of most security professionals. Last night Mr. Ben Gvir’s supporters greeted him with chants “death to the terrorists.” They reportedly were instructed to avoid frequent cries of  “Death to the Arabs.”

All that is a far cry from Mr. Netanyahu’s message in his victory speech last night, in which he vowed to reunite the country. “We will work to lower the flames in the public discourse,” Mr. Netanyahu said. “We will strive to mend the fissures in a society ripped apart.” That suggests Mr. Netanyahu would need to marginalize Mr. Ben Gvir, blunt his instinct for mayhem, and to reunite with some centrist former allies. 

Ay, there’s the rub, too. For such former Likud members and others who could potentially coalesce with Bibi are likely to eschew any coalition that would include Mr. Ben Gvir. It’s us or him, they’re likely to say. Mr. Netanyahu’s government, therefore, may well be beholden to a figure who was a) until recently shunned by the majority of Israelis and b) greeted last night by crowds shouting “Hoo-hah, here’s the next prime minister.”

It’s a moment to bear in mind that Mr. Netanyahu is still on trial on various charges of corruption. We tend to see this as a symptom of the American Disease, a penchant for fighting political battles with criminal prosecutions. The prosecution is the scandal. Yet we don’t gainsay the danger that the criminal case could still make Mr. Netanyahu vulnerable to political attack from the right and left. Which makes his triumph Tuesday that much more impressive.