Former Prime Minister Ehud Barak announced Wednesday the establishment of a new party, saying Prime Minister Benajmin Netanyahu's regime, with its "corrupt and messianic elements," must be toppled.

"These are the darkest days we have known," Barak told a press conferece, arguing the decision to call new election was solely meant to "disrupt the legal procedure" against Netanyahu in his bribery cases.

Accoring to Barak, Netanayhu's "time as a political leader is over." He also called on other Israeli political leaders to join forces ahead of the September 17 election, particularly "his brothers in arms" Benny Gantz and Yair Lapid from Kahol Lavan party.

Barak, also the former chairman of the Labor Party, is expected to base his new platform to be formally established in the upcoming days on Haatzmaut, a party he formed when splitting from Labor in 2011.

In order to make a grand union with left-wing parties, Barak will need Itzik Shmuli as Labor leader and Nitzan Horowitz as leader of Meretz. The Labor primary will take place on July 2 and the Meretz primary will take place on Thursday this week.

Shmuli already announced on Wednesday that he will work towards a merge with Barak's party if he is elected head of Labor. According to estimates, if Tamar Zandberg continues leading Meretz, such a merge would be difficult to accomplish as Barak would be rejected by the party's Arab supporters - which according to April 2019 election, constitute around a quarter of Meretz voters.

According to a poll released by Israeli Channel 13 news on Wednesday, a party headed by Barak would receive six out of 120 Knesset seats in the next election. The poll was conducted before Barak's announcement. It furthermore predicted 49 seats for the center-left bloc, 40 seats for the right-wing bloc, seven seats for Avigdor Lieberman's Yisrael Beiteinu, 12 seats for ultra-Orthodox parties Shas and United Torah Judaism, and 12 seats for Arab-majority party The Joint List.

Barak was joined by Yair Golan, a general in reserves, and Kobi Richter, cofounder of Medinol, which makes stents and who also chairs the Darkenu organization, which supports the two-state solution for the Israeli-Palestinian conflict.

Another apparent joiner is Prof. Yifat Biton, who ran in the April 2019 election with Gesher, the party founded by Orly Abekasis. Gesher didn’t pass the electoral threshold in the last election.

In recent weeks Barak has been deliberating whether to try to regain the leadership in Labor or to launch a new political entity. His plan appears to be based on two stages: founding an independent party that draws on support in the center and left of the political map, and gaining partners, possibly joint lists with the Labor Party itself, to create a significant centrist party.

Barak also reportedly heavily pressured to two former colleagues in politics, Tzipi Livni and Yoel Hasson, to join him too.

It seems Barak isn't trying to attract votes from the right side of the map, but to reorganize the resources on the left after the poor showing of both the Labor Party and Meretz in the April election, say sources who talked with him recently.

Nitzan Horowitz, a contender to lead Meretz, wouldn't comment on whether he met with Barak or whether Meretz under his putative leadership might join forces with the new party.