JERUSALEM — They joined forces three decades ago, rising to power as a political odd couple like none Israelis had ever seen.
Benjamin Netanyahu was the silver-tongued, M.I.T.-educated sophisticate. Avigdor Liberman was a penniless former bar bouncer from Moldova, happy to be the hatchet man.
Ever since, the two right-wing politicians have alternately aided and tormented each another, like lovers locked in an abusive relationship.
Now they are barreling toward a climactic denouement, as Israel votes in a national election on Tuesday that could reshape the country’s political landscape and determine whether Mr. Netanyahu, Israel’s longest-serving prime minister, will be sent into retirement, and whether Mr. Liberman, his former deputy, is launched on a path to one day replace him or into political oblivion.
“Such a fight, between two people who’ve been like one entity, one man — a fight between two twins — I don’t remember, ever,” said Shalom Yerushalmi, a veteran political writer at the news site Zman Yisrael.
Mr. Liberman is not popular enough to replace Mr. Netanyahu himself but his party is expected to win enough seats to make him a kingmaker, capable of throwing the premiership to someone else.
Benny Gantz, a centrist former military chief, is Mr. Netanyahu’s main challenger and poised to become prime minister if Mr. Netanyahu loses.
But it was Mr. Liberman’s refusal to join a coalition with Mr. Netanyahu’s ultra-Orthodox Jewish partners in the last election, just five months ago, that denied Mr. Netanyahu a majority and forced the unprecedented do-over election on Tuesday.
The gambit turned Mr. Liberman into the champion of secular Israelis and recast this election as one in which the usual battle of left against right has been overshadowed by the one between the secular and the religious.
While there is a rough consensus in Israel on the vital issues of national security and relations with the Palestinians, Mr. Liberman has exposed a fault line on the role of religion, appealing to secular Israelis fed up with the special benefits and subsidies accorded the ultra-Orthodox.
The high stakes and extraordinarily personal rivalry have turned what might have been a tedious midsummer campaign into a thrilling cage match.
Mr. Netanyahu has denounced Mr. Liberman as “part of the left,” calling him a serial toppler of right-wing governments. Mr. Liberman accuses Mr. Netanyahu of fostering a personality cult while lacking the backbone to keep his political promises.
“They are a couple who have had a lot of fights, but they never went to the rabbinate to file for divorce,” said Yehuda Ben Meir, a former lawmaker now with the Institute for National Security Studies in Tel Aviv. “Now, it’s different. If Netanyahu has given up on Liberman and Liberman has given up on Netanyahu, we face a real, serious possibility of change.”
Yet both politicians have displayed enough pragmatic flexibility over the years that Israelis do not rule out the possibility that, for all their knife-throwing now, they could wind up back together again once all the votes are in.
Chemistry and Clean Shirts
They first met in Jerusalem in 1988, when Mr. Netanyahu, then seen as more American than Israeli, was plotting his entry into Israeli politics near the end of his tenure as ambassador to the United Nations in New York. Mr. Liberman, an immigrant from Moldova with a thick Russian accent, had shown a knack for grass-roots organizing.
Mr. Netanyahu needed a brass-tacks operative and felt a “chemistry” between them, he later recalled; Mr. Liberman was initially happy to be the junior partner, putting his wiles to use in the service of the camera-ready Netanyahu.
The two soon became inseparable, with Mr. Liberman guiding Mr. Netanyahu in and out of weddings, bar mitzvahs and local party offices, always ready with a sandwich or a clean shirt.
When Mr. Netanyahu won the Likud party chairmanship in 1993, becoming the party’s public face, he made Mr. Liberman director-general, the back-room boss. Mr. Liberman took to the task with zeal, firing workers and slashing debts. And when Mr. Netanyahu shocked Israel by edging out Shimon Peres to become prime minister in 1996, he made Mr. Liberman director-general of his office, investing him with power and prestige.
While Mr. Netanyahu played the leading man, Mr. Liberman was the heavy, and he soon became a target for the Likud’s so-called princes, scions of the party’s founding generation. He saw them as spoiled elitists expecting to inherit the leadership without getting their hands dirty. They bridled at his brashness and never let him forget where he was from.
“Every day they remind me that I’m ‘Vladimir,’” he complained on a prime-time talk show — referring to his depiction on a comedy show as a bloodthirsty bully by that name — “that I’m a thug, that I belong to the Russian mafia, that I’m a K.G.B. agent, that I’m Rasputin, Zhirinovsky. I, who started out as a porter and a bouncer in a bar, I’m not ashamed of anything!”
In 1997, when the princes accused of Mr. Liberman of dirty tricks on the prime minister’s behalf, Mr. Netanyahu disavowed his actions.
“That was the first betrayal,” said Anna Ravya-Barsky, a political analyst for Israel’s Russian-language news media.
Mr. Liberman called a news conference and quit.
“He felt Netanyahu didn’t believe in him anymore,” said Beny Bitton, the mayor of the desert city of Dimona and an early friend of Mr. Liberman’s. “The dirty work was done, so the servant could go home.”
Mr. Liberman went into business, investing and making deals in several countries with the backing of wealthy friends.
In late 1998, he was sipping a beer in Budapest, he later wrote, when he received a frantic call from the prime minister’s secretary. Mr. Netanyahu’s government was divided over concessions to the Palestinians and in danger of falling. Mr. Liberman was urgently needed in Jerusalem.
Mr. Liberman rushed back to Israel and straight to Mr. Netanyahu, offering his help around the clock if need be, he wrote. But Mr. Netanyahu never followed up, and Mr. Liberman heard rumors that Netanyahu aides considered Mr. Liberman an “electoral liability” who should be kept at a distance.
“I was shocked. I felt humiliated,” Mr. Liberman wrote in his 2004 memoir, “My Truth.” “I immediately understood that if I don’t do something drastic to prove to myself and others who I really am, I would carry for the rest of my life the stigma, a mark of Cain, the label of being an uncouth thug, a man who knows how to pull strings behind the scenes and always engages in manipulations.”
He created his own party, Yisrael Beiteinu, Hebrew for “Israel is our home.” It won four seats in 1999 as Mr. Netanyahu was driven from office.
Quit, Return, Repeat
With each man leading his own party, the bickering became public. Mr. Liberman took pot shots at Mr. Netanyahu even as he joined him in coalitions that kept Mr. Netanayhu in power. Mr. Netanyahu appointed Mr. Liberman to posts as vital as foreign and defense minister while forever trying to put him in his place.
Mr. Liberman has been a coalition partner and minister in six governments since 2001. He quit or was fired five times, in most cases in disputes over policy toward the Palestinians.
His party peaked in the 2009 election, which brought Mr. Netanyahu back to power, becoming the third-largest party with 15 out of 120 seats in Parliament. With that showing, Mr. Liberman commanded a high price: Mr. Netanyahu named him foreign minister and deputy prime minister.
In short order, Mr. Liberman was complaining that Mr. Netanyahu was slighting him, shrinking his budgets and cutting him out of weighty foreign-policy matters and diplomatic appointments. For his part, Mr. Liberman was showing up Mr. Netanyahu, giving a United Nations speech that broke with the prime minister’s stance on the Palestinian conflict and accusing him of weakness on other issues.
On one level, the criticism could make Mr. Netanyahu look weak and Mr. Liberman stronger to the right-wing voters they both needed. But Mr. Liberman’s demands to place obstacles in the way of progress with the Palestinians, like a loyalty oath for Arab citizens or a referendum on any peace deal, may also have been welcome to Mr. Netanyahu, giving him political cover to drag his feet.
Despite their differences, they joined forces to run together in 2013, with Mr. Liberman as No. 2, though he broke up the partnership a year later.
In 2015, Mr. Liberman began to stake out the position that led to this spring’s debacle, refusing to join Mr. Netanyahu’s government because he had acceded to nearly all of the ultra-Orthodox parties’ demands even before sitting down with Yisrael Beiteinu, which opposed a number of them.
Still, Mr. Liberman joined Mr. Netanyahu’s government a year later in exchange for the defense ministry, gaining the security credentials he had long needed to be taken seriously as a potential premier.
Despite promoting him, Mr. Netanyahu often stymied and humiliated Mr. Liberman, ignoring or overruling his more bombastic policy positions, from the death penalty for convicted terrorists to toppling Hamas. Associates say Mr. Liberman believes he has been denied adequate credit for opening doors for Israeli diplomacy across Africa and Latin America. They also say he has been more instrumental in Mr. Netanyahu’s political success than the prime minister’s longstanding nickname, “the magician,” would suggest.
Mr. Netanyahu overruled Mr. Liberman to pursue a policy of containment in Gaza, hastily agreeing to cease-fires with Hamas and facilitating transfers of Qatari cash to maintain the fragile calm. Mr. Liberman quit in protest last November, helping to precipitate the April elections.
Mr. Netanyahu and Mr. Liberman both declined requests for interviews.
‘A Balance of Terror’
Given such friction, many have speculated about the deep secrets that could explain Mr. Liberman and Mr. Netanyahu’s inability to quit one another.
“Their partnership is based on them knowing each other’s secrets,” said Orit Galili-Zucker, a political consultant who worked for Mr. Netanyahu from 2010 to 2013. “There is a balance of terror between them, because they know everything there is to know about each other from the very beginning.”
Mr. Netanyahu is now facing possible indictment in three corruption cases. The attorney general is to decide whether to press charges over accusations of bribery, fraud and breach of trust after a hearing in October.
But Mr. Liberman and his party have also been plagued by corruption allegations.
One persistent rumor involves the main case against Mr. Liberman, who was accused of only pretending to divest from his businesses when he entered government in 2001, and was suspected of secretly reaping millions from wealthy foreigners, and of money laundering. In 2009, the police recommended his indictment on corruption charges.
Mr. Netanyahu appointed an attorney general — Yehuda Weinstein, a criminal-defense lawyer — who closed the case in 2012 without charges, citing a lack of evidence.
The rumor was there had been a deal.
In May, Mr. Netanyahu’s son Yair resurrected it.
“Here is a scoop for you,” Yair Netanyahu wrote on Twitter in May, shortly after Mr. Liberman dashed the older Netanyahu’s hopes of forming a government. “That was his most important coalition demand in 2009.”
Swift denials followed from all parties. A Netanyahu family spokesman said that Yair was in high school at the time, had no inside knowledge and was just repeating gossip. Mr. Weinstein has called Yair Netanyahu’s claim nonsense and said that he would have come to the same conclusion about the case today.
But for others, the issue has never been laid to rest — including Avia Alef, who headed the department of economic crimes in the Israeli state attorney’s office until 2013. She says that Mr. Weinstein dragged out the investigation and cast doubt on the evidence to weaken the case as witnesses disappeared, lost their memory or died.
“From the beginning it was about killing the case softly,” she said in an interview.
Throughout Mr. Liberman’s 17 years of legal troubles he was never betrayed by his close associates, though some went to prison themselves. The same cannot be said for Mr. Netanyahu, whose corruption woes owe heavily to former top aides who turned state’s evidence.
Despite Mr. Netanyahu’s weakened state, aspiring Likud leaders have shrunk from trying to depose him, raising the possibility that it could take Mr. Liberman to administer the fatal blow.
Though he has said he could abide the centrist Mr. Gantz as prime minister in a unity government, it is easier for many Israelis to imagine the ambitious Mr. Liberman trying to parlay his leverage into an agreement to share the premiership with Mr. Netanyahu on a rotating basis.
Such a once-unthinkable prospect would at last give the magician and his erstwhile assistant equal billing.