Avigdor Lieberman entered Israeli politics as a loyal protégé of Prime Minister Benjamin Netanyahu. Now, the maverick politician could be the one to topple his former mentor. Lieberman, a burly, tough-talking immigrant from the former Soviet Union, forced Israel’s unprecedented second election of the year and is poised to be the kingmaker again. Polls suggest Netanyahu won’t be able to form a coalition government without Lieberman’s support. Lieberman has played hard to get. “I don’t have to join at any cost,” he told Channel 12 news over the weekend. “The prime minister’s policy is simply submission to terrorism.” For years, Netanyahu and Lieberman have had a roller-coaster relationship. Lieberman, once Netanyahu’s chief of staff, has held a series of senior Cabinet posts and was often a staunch partner. But he’s has also been a rival, critic and thorn in Netanyahu’s side. In a high-stakes gamble, he passed up the post of defense minister in Netanyahu’s government following April’s election, leaving the prime minister without a parliamentary majority and forcing the Sept. 17 do-over vote. Their dispute, over what Lieberman says is excessive influence of ultra-Orthodox religious parties, has become a central issue in the current campaign. Lieberman says he will insist on a secular unity government between Netanyahu and his main challenger, Benny Gantz, in order to push out ultra-Orthodox parties. But Netanyahu says his former ally’s real goal is to oust him from office, and Lieberman is suddenly discovering newfound support from those who hope he does just that.