Netanyahu, like Israel’s shreds of justice, is being challenged by a former protege

But after failing to challenge Mr. Netanyahu for Likud’s leadership in late 2019, Mr. Saar broke away to form his own party called New Hope. That group offers a right-wing alternative to Mr Netanyahu for the upcoming election on March 23, the fourth parliamentary vote in less than two years.

In contrast to the Israeli elections of the past decade, where Mr. Netanyahu fended off challenges from the left and the center, Mr. Saar is facing a serious challenge to his former mentor from the right.

That poses a significant threat to Mr. Netanyahu, who has been criticized for his handling of the coronavirus pandemic and his corruption process. If Mr Saar can continue to siphon Mr Netanyahu’s support among right-wing parties in parliament, he could block the prime minister’s return to office.

“Everything is paralyzed,” said Mr Saar in an interview in his Tel Aviv apartment, where he lives with his wife and two young children. Mr. Netanyahu “puts his personal interests above the welfare of the country,” he added.

Whether voters will place their trust in an untested leader like Mr Saar is unclear. Mr. Netanyahu, known as Bibi, has been in power for 15 years, through two wars with Hamas militants in Gaza and heightened tensions with Iran. In recent months, Mr. Netanyahu has been involved in negotiating diplomatic standardization deals with Arab neighbors in the Gulf and is leading the fastest rollout of the Covid-19 vaccine in the world.

The donors of Mr. Netanyahu assign Mr. Saar as a “political opportunist” who left Likud after losing support in the party.

Saar gathers a group of stragglers who shout ‘No Bibi’ from the stands while the Prime Minister leads the revolutionary ‘Operation Return to Life’ vaccination program that is a model for the world, said a Likud party statement, referring to the Israeli vaccination campaign.

Mr Saar’s political positions are similar to those of Mr Netanyahu. He is a staunch supporter of the Jewish settlements in the West Bank that expanded under Mr. Netanyahu and have been criticized abroad, including in President Biden’s past.

Mr Saar does not support a construction freeze or the creation of a Palestinian state, but would honor Mr Netanyahu’s recent pledge not to annex parts of the West Bank as part of the diplomatic standardization agreements. Mr Saar also opposes a US return to the 2015 Iran nuclear deal, which Mr Biden has said he wants to renegotiate.

While Mr. Saar doesn’t deviate much from Mr. Netanyahu’s policies, he says he would bring a fresh start to the relationship with the new US president. “I can deal with the Biden administration better than Netanyahu and do that while protecting our national interests and without taking anything from the past that might disrupt that,” he said.

Mr. Netanyahu’s relationship with the Obama administration was tense, in part because of the US’s nuclear deal with Iran, an unshakable rival to Israel. In previous elections, Mr. Netanyahu campaigned with huge billboards showing photos of him shaking hands with former President Donald Trump and calling the Republican leader Israel’s greatest friend ever in the White House.

“Even though they are from different political perspectives, he is not Netanyahu,” said Martin Indyk, a leading member of the Council on Foreign Relations. “Biden will want to have a positive constructive relationship with the Prime Minister of Israel.”

Although Mr. Saar is taking some of the supporters away from Mr. Netanyahu, Likud is expected to remain the largest party in the Knesset, the Israeli parliament. The Yesh Atid party, under centrist Yair Lapid, is also rising in the polls, complicating Mr Saar’s bid to frame the upcoming vote as a right-wing contest.

The role of ultra-Orthodox religious parties could be important in the race between Messrs Netanyahu and Saar. Mr. Netanyahu is counting on them for political support. Mr Saar has not ruled out sitting with them in a future government, but so far those parties have indicated that they will continue to support Mr Netanyahu.

For both politicians, navigating the support of the ultra-Orthodox is politically complex.

Israel’s ultra-Orthodox communities have opposed the restrictions of the coronavirus and violently clashed with police during protests against them. That has sparked anger among other Israelis and frustration among public health officials, who believe the ongoing rule violation is undermining coronavirus efforts.

To become prime minister, a candidate must bring together a coalition with a majority of 61 seats in the Knesset. A recent poll by an Israeli radio station shows that New Hope wins 17 seats against Likud’s 30. In that scenario, Mr. Netanyahu would fail to form a governing coalition as a number of parties refuse to form a coalition with the prime minister.

“Until Saar broke, you reluctantly said Netanyahu is the only game in town,” said Reuven Hazan, a professor of political science at the Hebrew University in Jerusalem. “Now Netanyahu is suddenly surrounded by enemies.”

The loss of Israel’s highest government office would push Mr. Netanyahu into dangerous territory. He was charged last year with bribery, fraud and breach of trust over allegations that he accepted expensive gifts from wealthy businessmen in exchange for official favors and offered two media moguls regulatory and financial benefits in exchange for positive press coverage. He denies wrongdoing. He failed to obtain parliamentary immunity that would have protected him from prosecution during his tenure last year. His trial will resume next month.

If Mr. Netanyahu does not return as prime minister, he cannot serve in a governing coalition due to an Israeli law requiring ministers to resign if charged. That law does not apply to prime ministers. Such a setback would also complicate any attempt by loyalists to pass a law that would protect Mr. Netanyahu from trial while serving as prime minister.

Daniel Tarlow, a 48-year-old who runs a catering business and lives in the Jewish settlement of Elazar in the West Bank, said he would support Mr Saar this time instead of Mr Netanyahu because he thinks the prime minister has not helped. small businesses during the pandemic.

“I’m fed up with his politics and gimmicks,” said Mr Tarlow of Mr Netanyahu. “I take Saar on his word that he is an authentic Likud politician … If you were put aside by Bibi, it means there is enough content for you.”

—Dov Lieber contributed to this article.

Write to Felicia Schwartz at [email protected]