JERUSALEM — Israeli Prime Minister Benjamin Netanyahu’s strongest challengers in an election in April joined forces on Thursday, adding more potency to the centrist candidates’ bid to end the right-wing leader’s decade in power.

In anticipation of the announcement of a new alliance between former military chief Benny Gantz’ Resilience party and ex-Finance Minister Yair Lapid’s Yesh Atid faction, Netanyahu engineered a merger of far-right parties on Wednesday that could help him build a governing coalition after the ballot.

Resilience, in a statement, said Gantz, Lapid and Moshe Yaalon, a former defense minister, “decided to establish a joint list that will comprise the new Israeli ruling party”.

Gantz and Lapid, who met overnight, agreed on a “rotation for the prime minister’s post” in which Gantz would hold office for the first two-and-a-half years of a new government’s term before Lapid took over.

In their campaigns, both candidates have portrayed Netanyahu, who will become Israel’s longest-serving prime minister this summer if he wins the April 9 ballot, as haughty with power and criminally corrupt.

But even as Netanyahu faces possible indictment in three corruption investigations, opinion polls have predicted his Likud party will take about 30 seats in the 120-member parliament, putting him on track to form a rightist coalition similar to the one he now heads.

Netanyahu denies any wrongdoing.

Resilience and Yesh Atid have been trailing Likud by a wide margin, in second and third place. But the surveys also predicted a much tighter race and a possible upset should Gantz, 59, and Lapid, 55, team up and then form a centrist and left-wing parliamentary bloc larger than a Likud-led alliance.

Yuli Edelstein, speaker of the Israeli parliament and a top member of Likud, said the centrist merger made it more imperative for the right-wing to present a “united and strong” front.

“Any alternative will set Israel back by decades in terms of its economy and security,” he wrote on Twitter.

While Gantz and Lapid worked out their deal, Netanyahu helped negotiate the merger of two far-right parties, Jewish Home and Jewish Power, that could give followers of the late anti-Arab rabbi, Meir Kahane, a stronger voice in politics and help the prime minister in coalition-building.

Netanyahu has vowed to remain in office even if Israel’s attorney general decides to accept police recommendations to indict him in the corruption probes. But political commentators have said coalition partners might press for him to step down.

The prime minister is suspected of wrongfully accepting gifts from wealthy businessmen and dispensing favors in alleged bids for favorable coverage in a newspaper and a website. — Reuters