Tzipi Livni and her Ha'Tnuah party joined forces with Issac Herzog and the Labor party to run on a joint ticket titled the "Zionist Union" ticket in the March 2015 elections. The two leaders agreed on a rotation system, should they be victorious, in which Herzog would serve as Prime Minister for the first two years of the term, followed by Livni. The day before the election, on March 16, 2015, Livni announced that the rotation schedule that she and Herzog had designed was going to be scrapped, in an apparent last minute attempt to gain swing votes. Political rivals lambasted the decision, saying that Livni and Herzog were “panicking”.
Netanyahu's lawyer, attorney David Shimron, and Likud's Youth chairman, David Shain, accused the "Zionist Union" ticket of systematically violating multiple Israeli election laws on February 5. They accused the Laborand Ha'Tnuah parties of "raising money, engaging in organizational coordination and engaging in propaganda," and stated that the Zionist Camp ticket "is encouraging people to vote against Likud – in other words, it is engaging in forbidden propaganda." The complaint alleges that the party has been illegally using millions of Shekels that have been coming from NGO's and has been submitted to the Central Elections Committee, who will decide if the claims have any validity. Included in the complaint are accusations that the Labor and Ha'Tnuah parties "attempted to buy power with money... millions of dollars that come from leftists abroad are being funneled to finance the campaign to topple Benjamin Netanyahu and Likud." The Zionist Union party denied these accusations.
Polls in the week leading up to the election put the Labor/Ha'Tnuah Zionist Union ticket slightly ahead of Netanyahu's Likud party, winning a predicted 25 or 26 seats to Likud's predicted 21 or 22.
On March 18, 2015, the final election results came in and it was revealed that Netanyahu and his Likud party had beaten the Zionist Union ticket of Livni and Herzog. The Zionist Union ticket received enough votes for 24 out of 120 seats in the 20th Knesset, coming in second place.