On Sunday afternoon, after insisting for the past six months that under his leadership Labour would attract a new type of voter, Amir Peretz was forced by his fellow Knesset members to admit that the plan had failed in the election in September.

Worse, if the polls were anything to go by, the next election on March 2 could damn Labour to oblivion.

Once Mr Peretz made that admission, it was just a question of technicalities until, together with Meretz leader Nitzan Horowitz, a joint list of candidates for the two parties was agreed.

Mr Peretz had believed that his Mizrahi working-class roots, along with an alliance with the tiny Gesher party — led by Orly Levi-Abekasis, daughter of Likud grandee David Levy — would help Labour break new ground.

But the facts on the ground were that Labour failed in September to improve on its dismal showing in the April election: in both, the party won just six seats, the worst showing in its history.

And the polls in recent weeks have the party hovering just above the electoral threshold of 3.25 per cent, just like Meretz.

Yet still Mr Peretz was loath to give up his vision for a new social-democratic platform spanning the left-right divide.

But his MKs were firm with him and the implied threat was that if he wouldn’t give in, they would defect en-masse to join Meretz.

Mr Peretz duly did so with one condition: Ms Levi-Abekasis, who four years ago was a member of the nationalist Yisrael Beiteinu party, would join them too.

“There’s no choice,” he finally admitted. “We have to unite with Meretz.”

For Mr Horowitz, who has been arguing for a merged list even before he became Meretz leader in June, it was simple.

He was prepared even to give the second spot on the list which should have gone to him to Ms Levi-Abekasis to sweeten the deal and agree to Labour-Gesher having six of the ten top spots.

At the front of both party leaders’ minds is the assumption, backed up by polling, that in the upcoming third consecutive election, many centre-left voters will be so eager to get rid of Prime Minister Benjamin Netanyahu that they will vote for Blue & White, even if they are more ideologically aligned with Labour or Meretz.

Meretz is used to facing the electoral threshold afresh in every election, but for Labour, the party which founded Israel and ruled the state for a total of 35 years, this is a new predicament and a bitter pill for Mr Peretz to swallow.

While fielding one list of candidates, the two parties will remain independent.

Both sides hope that in the future Blue & White will struggle to retain its popularity, as all Israeli centrist parties have in the past.

Meanwhile, they will have to hope that Blue & White focuses its campaign on enticing voters from the right, rather than hoovering up more of theirs.

Blue & White’s leader Benny Gantz is the biggest winner, as it is now almost guaranteed that no opposition parties will fail to cross the threshold.

Suddenly, the right-wing looks more splintered and indeed its leader Mr Netanyahu is one of the losers, since his chances of winning a majority for his coalition have been greatly reduced.

The other big loser from the merger is the popular MK Stav Shaffir, who only six months ago came second to Mr Peretz in the Labour leadership race.

Shortly after failing to convince Mr Peretz to merge lists with Meretz before the September election, she defected to form with Meretz and ex-generals Ehud Barak and Yair Golan, the Democratic Camp list which won five seats.

But she quickly fell out with her Democratic Camp colleagues and when the party leaders drew up the joint list this time, there was no longer a spot for her on it.