The Zionist Union’s Tzipi Livni announced Monday evening that she would give up the rotation of the premiership with the slate’s leader, Isaac Herzog, an agreement the two made months ago when her Hatnua party merged with his Labor Party.

In response, Prime Minister Benjamin Netanyahu said the party was “panicking,” while Yesh Atid party leader Yair Lapid and Jewish Home party leader Naftali Bennett said the move indicated the Zionist Union was planning to form a unity government with Netanyahu’s Likud. That claim was subsequently rejected by Herzog as “claptrap.”

The bombshell came 12 hours before polling stations were set to open, in an apparent last-ditch effort to garner additional votes.

Livni said the rotation agreement ought not interfere with her party’s main task: replacing Netanyahu’s Likud party.

In a response to the announcement, Netanyahu told Channel 2 that the decision reflected the Zionist Union’s “panic” — an accusation echoed by Herzog, who in turn said Netanyahu was the one “panicking.”

Netanyahu told the TV station that the move proved two things: “One, that they’re lying. Either they lied earlier [when they announced the rotation], or they’re lying now. And the second thing is that they can’t deal with any pressure. They can’t deal with the pressure of the polls; how will they be able to deal with international pressure?”

Shortly after the announcement, Bennett predicted that the decision to give up the rotation signaled that the Zionist Union would form a unity government with Likud, implying that a vote for his right-wing party could help prevent such an outcome. Lapid, similarly, told the TV station the move signaled that a national unity government between the two large parties, as well as the ultra-Orthodox parties, was in the works.

Herzog denied the allegations as “nonsense” in a telephone interview with Channel 2. He said the decision was not a matter of “last-minute pressure,” and that “Livni nobly and bravely told me this initially on Saturday.

“Ultimately, she approached me today and told me honestly — if the rotation is in some way an obstacle to the establishment of the government, I won’t stand in the way,” he said.

Livni, No. 2 on the Zionist Union list, had initially agreed to a two-year rotation of the premiership if the Zionist Union was tasked with forming the coalition. The Hatnua-Labor merger was criticized by members of the Labor Party, who said that Livni was getting more than she offered to the party. However, the political union, and subsequent re-branding of the party, sparked a surge in the polls.

On Sunday, Haaretz reported that during a Zionist Union campaign meeting, Livni said she was willing to forgo the rotation. But strategist Reuven Adler opined that such a move, announced so close to the election, would be detrimental.

Two hours before the announcement, Herzog emphatically denied that the two were set to cancel the rotation agreement. “There was no discussion about [whether to cancel the rotation] in the past week. It’s not on the agenda, period. The partnership between Livni and me brought us to [where we are] today. It is an important partnership,” Herzog told Army Radio.

The Likud party had bashed the alliance between Herzog and Livni, a former Likud member herself. Throughout the campaign, the party repeatedly commented on Livni’s “disappearance” from the public eye, a move that she explained several weeks ago as a tactic to keep the spotlight on Herzog, who, she said, was less well-known than she.

Times of Israel staff contributed to this report.