Israel's divided government collapsed early Wednesday, triggering the country's fourth election in under two years and bringing an unprecedented threat to Prime Minister Benjamin Netanyahu's lengthy grip on power.

Netanyahu, who is used to labelling his opponents as weak leftists, finds himself confronted by a trio of disgruntled former aides who share his hard-line ideology, led by a popular lawmaker who recently broke away from the prime minister's Likud party.

Whether Netanyahu can fend off these challengers or not, the country is almost certain to be led by a right-wing politician opposed to concessions to the Palestinians, complicating hopes of the incoming Biden administration to restart peace talks.

The prospects of Israel's center-left bloc appear worse than in previous contests because its leader, Defense Minister Benny Gantz, entered into the ill-fated alliance with Netanyahu. Gantz has lost the support of much of his disappointed base, and the bloc has been left leaderless.

Netanyahu and Gantz formed their coalition last May after battling to a stalemate in three consecutive elections. They said they were putting aside their personal rivalry to form an "emergency" government focused on guiding the country through the health and economic crises caused by the pandemic.

Under the deal, Gantz assumed the new role of "alternate prime minister" and was assured he would trade places with Netanyahu next November in a rotation agreement halfway through their term. The immediate cause of the collapse was their failure to pass a budget by the midnight Tuesday deadline. That caused the parliament to automatically dissolve and set new elections for late March.

But the deeper cause was their troubled partnership, which was plagued by mutual hostility and mistrust from the outset. For seven months, Gantz has suffered a number of humiliations and been kept out of the loop on key decisions, such as a series of US-brokered diplomatic agreements with Arab countries.

Netanyahu accuses Gantz's Blue and White party of acting as an "opposition within the government." At the heart of this dysfunctional relationship is Netanyahu''s corruption trial. Gantz has accused Netanyahu of undermining their power-sharing deal in hopes of remaining in office throughout his trial, which is to kick into high gear in February when witnesses begin to take the stand.

He and other critics believe Netanyahu ultimately hopes to form a new government capable of appointing loyalists to sensitive positions who could grant him immunity or dismiss the charges against him.

"A criminal defendant with three indictments is dragging the country to a fourth round of elections," Blue and White said Tuesday night. "If there wasn't a trial, there would be a budget and there wouldn't be elections."

Netanyahu is charged with fraud, breach of trust and accepting bribes in a series of scandals in which he is accused of offering favors to powerful media figures in exchange for positive news coverage about him and his family. His legal troubles, and questions about his suitability to govern, have been the central issue in the string of recent elections.

"The ongoing political crisis will continue as long as Mr Netanyahu remains prime minister and no government can be formed without him," said Yohanan Plesner, a former lawmaker who is president of the Israel Democracy Institute.

"I think it is quite safe to assume that this won't end until either Mr Netanyahu is replaced or if he finds a way, through legislation or political manoeuvring, to either put his trial on hold or suspend it altogether," he said.

In the previous three elections, Netanyahu was unable to put together a majority coalition with his traditional religious and nationalist allies. Yet he controlled enough seats to prevent his opponents from cobbling together an alternate coalition.

According to recent opinion polls, that equation may be changing, with a number of rivals poised to control a parliamentary majority without him.

Those rivals are led by Gideon Saar, a stalwart in Netanyahu's Likud who announced this month that he was breaking away and forming a new party. Saar, who once served as Netanyahu's Cabinet secretary, has accused the prime minister of turning the Likud into a "personality cult" focused on ensuring its leader's political survival.

If elections were held today, Saar's party would finish second behind the Likud, appearing to give him a veto over a Netanyahu-led government, according to polls. Saar has vowed he will not serve under Netanyahu.

Naftali Bennett, another former aide who had a falling out with Netanyahu, leads a religious right-wing party that also has surged in the polls. And Avigdor Lieberman, Netanyahu''s former chief of staff and a longtime Cabinet minister who now leads his own party, also says the prime minister is unfit to lead.

All of these rivalries are more personal than ideological, meaning that Israel's next government — led by Netanyahu or not — almost certainly will have a right-wing ideology that opposes Palestinian independence and supports continued Israeli settlement construction in the occupied West Bank.

The recent polls indicate that Gantz, who appealed to left-wing voters in previous elections, may not receive enough votes to even enter the next Knesset.