PM Binyamin Netanyahu’s plan to split the Likud’s main political rival, Kadima, suffered a setback this week when Kadima’s Knesset members unanimously voted to turn down his offer to join a national unity government. But the political machinations of the past two weeks also revealed the weakness of Kadima chair Tzipi Livni’s leadership.

Mr Netanyahu had suggested that Kadima appoint two ministers without portfolios and have a representative in the select cabinet forums which deal with security matters. But Mr Netanyahu refused to change his government’s policies or open the agreements with existing coalition members. He also insisted that he would be the sole authority on any peace talks.

The PM was forced to make Kadima a formal offer after it emerged that he had been in intensive talks with a number of Kadima MKs over the possibility that they would break away from their party and join Likud.

Mr Netanyahu has made no secret of his desire to break up the party, which was founded by members of Likud — headed by Ariel Sharon — who had tried to bury his own political career.

Kadima leader Ms Livni refused to join a Netanyahu government nine months ago following the election, claiming that as the leader of the party that had received the most votes, she should be PM. Mr Netanyahu has been trying to entice Kadima MKs away from Ms Livni ever since.

MKs who were identified as “weak links” were, in recent weeks, offered junior ministerial positions and Knesset committee chairmanships for their defection. A new law, pushed through at Mr Netanyahu’s insistence, says that seven or more MKs can break away from their party and join another.

The secret talks with the “wobbling” MKs continued during the cabinet’s marathon meeting last week over the Shalit prisoner exchange. When this emerged, Mr Netanyahu was heavily criticised for “playing politics as usual” while the Shalit deal hung in balance.

He quickly made the offer to Ms Livni to join his government, with the aim of portraying himself as the nation’s unifier.

Mr Netanyahu did not offer Kadima any senior government posts, claiming that there was “no time for politicking” when national unity was so urgent. He cited the example of Likud leader Menahem Begin, who accepted similar terms when joining an emergency unity government in 1967.

At the same time, a number of Kadima members chose to attack Ms Livni’s leadership. Some, such as Othniell Schneller, demanded she join the government, while others, such as former minister Eli Aflallo, said that “Livni has failed both as party leader and leader of the opposition”. Her main rival within the party, Shaul Mofaz, who lost the leadership primary to her by a tiny margin last year, revived his calls for new primaries.

In the end it was the paltriness of Mr Netanyahu’s offer that saved the day for Ms Livni. The entire party, including her critics, agreed that the offer was “not serious” and supported a motion turning it down. But some of them added privately after the vote that this did not mean they were supporting Ms Livni and would continue to work for her replacement.