JERUSALEM — Benny Gantz, the former army chief, failed in his month-long attempt to put together a governing coalition Wednesday, prolonging Israel’s protracted political gridlock and making it likely that voters will have to endure a third national election in less than a year.

Gantz, who has rocketed to the top tier of Israeli politics, caused a stir in October when he became the first person other than Benjamin Netanyahu to be given a chance to form a government here in a decade. Twenty-eight days later, his mandate to try is expiring with no parliamentary majority in sight. After weeks of negotiation among Israel’s fractious parties, the deadline has come and gone, another way station to nowhere in the country’s year-long political stalemate.

Gantz said in a statement Wednesday that he had informed Israeli President Reuven Rivlin that it was not possible to form a government.

“I left no stone unturned. I sifted through every grain of sand,” Gantz said in a televised address. He accused Netanyahu, the prime minister, of negotiating not in good faith over a possible unity government but “with childish videos and slogans.”

For the next three weeks, the law allows any member of the Knesset, Israel’s parliament, a chance to do what Gantz and Netanyahu could not: cobble together the 61 votes needed to form a government. If this, too, falls short, as most analysts predict, the country’s deja-vu nightmare will continue with another election, probably in March.

“Israel is caught in a cul-de-sac,” said Daniel B. Shapiro, former U.S. ambassador to Israel and research fellow at the Institute for National Security Studies in Tel Aviv. “There just seems to be no workable coalition among the parties as they were elected.”

Israel is a country deeply divided, and not just along a single fault line but a spider web of them. A range of parties split on questions of religion, security and the role of Arabs in Israeli society are wrestling for influence. At the center is Netanyahu, a polarizing leader who is likely to face indictment on corruption charges by the end of the month.

“You have too many cross­cutting interests and personalities and a prime minister fighting for survival,” Shapiro said.

The breakdown in governance is roiling a country that has prided itself in recent decades on stable if raucous leadership. As the months have passed, concern has grown that budgets and planning are beginning to suffer at a time of growing tension in the region.

The Israeli military that Gantz used to lead has been busy in recent weeks conducting operations against militants in Gaza and Iranian military targets in Syria. But army officials, speaking on the condition of anonymity to talk candidly, say they need a government in place for long-term strategic planning and budgeting.

“Things are running by themselves, without the politicians,” said Aviv Bushinsky, a political commentator and former Netanyahu staff member. “That can be both good and bad.”

Analysts don’t know how to predict what the next phase will bring because they’ve never seen one like it. Never before has Israel’s parliamentary system had to trigger the coming 21-day free-for-all that allows for any lawmaker to play government builder.

Most say the dynamics that have so far stymied the politicians won’t change. As has been the case for months, all eyes will be on would-be kingmaker Avigdor Liberman, the hawkish former defense minister whose resignation from the government exactly a year ago helped spark the political uncertainty.

On Wednesday, Liberman announced that he would support neither a minority coalition led by Gantz nor a bloc of right-wing, religious parties led by Netanyahu. Both leaders had been trying to entice him into an arrangement, but both options appeared to conflict with his secular, right-wing ideology.

Liberman, head of the Yisrael Beiteinu party, has been a wild card since the first election this year, in April. After that vote, he refused to join a Netanyahu-led coalition because of its alignment with religious factions.

Since the September election, Liberman has refused to back either candidate, calling on Netanyahu and Gantz to bring their parties together in a secular unity government.

Liberman said in his news conference that he would not cooperate with a faction of Arab parties, which he has consistently referred to as a “fifth column.” This rules out the option of Gantz forming a minority government backed from outside the coalition by 13 Arab lawmakers. Liberman also reiterated his position of not joining a government with Netanyahu and parties representing ultra-Orthodox Jews and a group of Jewish settlers, which Liberman has called “messianic.”

In reality, most analysts say only Gantz or Netanyahu have a chance at getting enough support to prevail. All sides will be under pressure to make deals, as the idea of a third election is vastly unpopular among exhausted voters.

The 21-day window effectively evens the playing field between Gantz and Netanyahu, although Netanyahu has a slight edge because he has the support of 55 right-wing and religious Knesset members.

Gantz could give in and join Netanyahu in a national unity government. If this were to happen, it is likely that Gantz’s Blue and White party would disband. Gantz’s number two, Yair Lapid, formerly head of the Yesh Atid party, has stated that he will not join a government with a prime minister facing indictment charges. Moshe Yaalon, a former defense minister, has expressed the same. If these two remain outside, Gantz could realistically join Netanyahu with only 15 Knesset members.

If no deal is reached by Dec. 11, the third campaign will begin (or before, if the Knesset simply gives up and votes to dissolve itself earlier).

But would another trip to the ballot box change much? Polling so far suggests no great shift in the vote. But one thing would be different: If Israel’s attorney general hands down corruption indictments against Netanyahu as expected, the prime minister would be under an unprecedented legal cloud during the campaign.

“That’s the one thing that would be different in a third election,” said Shapiro. “Would that change votes? Would he even be eligible to run?”

Bushinsky, for his part, thinks someone will budge under the pressure, producing a compromise and a government sometime in December. If not, he predicts the third election will do the trick.

“We will not have a fourth one,” he said. “If we have a fourth one, Jerusalem will become a new bastille.”