Kadima chairman Shaul Mofaz officially changed hats from vice premier to opposition leader at 7 p.m. on Thursday when his resignation from the cabinet took effect.

Labor chairwoman Shelly Yechimovich sent an official letter of resignation as opposition leader to Knesset Speaker Reuven Rivlin earlier in the day.

“Due to the changes in the coalition and Kadima’s return to the opposition as its largest party, I am announcing the end of my tenure as opposition leader,” Yechimovich wrote.

A Labor spokeswoman explained that the letter was a formal step, meant to facilitate a smooth transition for Mofaz.

Mofaz’s decision to leave the government ended efforts by lawmakers in the party’s left flank to draft the seven (out of 28) MKs necessary by law to split the Kadima faction. Likud officials tried unsuccessfully to persuade five rebellious Kadima MKs on the Left to collaborate with rightist MKs Otniel Schneller and Yulia Shamolov Berkovich, who want to join the Likud.

Dovish Kadima MK Nino Abesadze denied a Channel 2 report claiming that she had decided to run with Labor in the next election. She confirmed that she did speak at a Labor event on Thursday, which was a “Hyde Park” forum attended by socioeconomic activists affiliated with Labor and Kadima.

“I said at the event that I am an MK in Kadima,” Abesadze said. “As for the next election, I have learned that in Israel you can’t plan anything more than 24 hours in advance.”