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WASHINGTON — Less than three months before Israel’s next election, Prime Minister Benjamin Netanyahu is looking unexpectedly weak. Until very recently, few people would have bet against his remaining prime minister. His party seemed strong, his ruling political bloc intimidating and his lead against challengers safe. But then came Nov. 6 — his “nightmare,” as political commentators have come to describe it.

In late October, Netanyahu had seemed to pre-empt his rivals with the surprise announcement that his own Likud Party and Foreign Minister Avigdor Lieberman’s Yisrael Beiteinu Party would merge their candidates’ lists for the Jan. 22 election. Today Likud and Yisrael Beiteinu are the second- and third-largest in the Knesset, with, respectively, 27 and 15 seats out of 120. Together, the idea was, they would be unbeatable against any rival party. Kadima, the largest party in terms of seats, is weak.

By last week, however, the move no longer looked so cunning. Netanyahu is still way ahead of the competition, but polls suggest that the new Likud-Beiteinu may be weaker than the sum of its parts. With some Likud voters skeptical of Lieberman’s in-your-face ways, and some Lieberman voters wary that Likud may be ideologically compromised, the merged party could get fewer votes than the two parties do now.

And then there was Nov. 6. In Netanyahu’s first setback of the day, his former chief of staff and long-time critic Naftali Bennett became the leader of Habayit Hayehudi, a religious-Zionist party in Netanyahu’s current coalition to which he likely would have wanted to remain associated.

And then there was the blow of Barack Obama’s re-election. Netanyahu apparently believed until the last minute that Mitt Romney would win. When he lost, Netanyahu became a target of mockery and criticism. Former Prime Minister Ehud Olmert, a potential rival in the January election, slammed him for “breaking all the rules” by “intervening” in the U.S. elections.

Later this week Olmert and the former Foreign Minister Tzipi Livni are supposed to disclose their plans for the January election. Both will face serious obstacles if they run. Last July Olmert was convicted of breach of trust, and prosecutors just announced they would appeal the parts of the verdict acquitting him on other charges. He is on trial again for yet more corruption charges in the so-called Holyland case. He doesn’t have a party yet. And voters don’t much like him.

Livni is more popular, but her tenure as the head of the Kadima Party was an astounding failure. Even though Kadima won the most votes in the 2009 election, she wasn’t able to stop Netanyahu from putting together a governing coalition. (In Israel, it isn’t the absolute number of parliamentary seats won that determines who runs the country but rather who can garner the support of 61 Knesset members.) Livni also proved ineffective as opposition leader, eventually losing the post to her rival Shaul Mofaz. By the time she resigned, Kadima was going up in flames.

Still, an Olmert-Livni alliance may be Netanyahu’s greatest threat. Many voters see the pair as the only possible remedy for a fractured center-left with no serious unifying candidate for the top job.

The duo’s chances certainly are better now that Netanyahu has made himself seem more vulnerable. His merger with Lieberman pushed him further to the right. Having to make do with the hawkish Bennett will push him even farther right. And, for some, Netanyahu’s bet on Romney will undermine the special relations between Israel and the United States.

Netanyahu should have run as Israel’s one viable centrist leader, its only responsible adult. But by rushing to protect himself from rivals who stood very little chance of defeating him, he only made their case stronger.