Yosef Lapid, a former justice minister who crusaded against Orthodox control over Jewish religious affairs in Israel, has quit the secularist Shinui, the parliament's third largest party.
A Holocaust survivor and veteran journalist with a flair for courting controversy, Mr Lapid led Shinui in the 2003 elections but today said his party had little chance in the the March general election.
Prime Minister Ariel Sharon's formation of the centrist Kadima Party last year undercut Shinui's middle-class support base and surveys predict the party may not take enough votes to win even one of the 120 seats in the Knesset in the March 28th poll.
"In its current configuration, Shinui does not deserve the public trust. A chapter in my life, a chapter I am proud of, is over and done with," Mr Lapid (74) told reporters.
He was justice minister under Mr Sharon, defending in the foreign media Israel's controversial barrier in the occupied West Bank. But he was fired from the cabinet in a 2004 budgetary dispute.
Shinui's support base was sapped by party infighting and failure to deliver on pledges to reduce state benefits to Orthodox institutions and break their control over Jewish religious rites, such as marriage, burial and conversion.
Some of Mr Lapid's more caustic comments about Israelis of Middle Eastern descent drew charges of bigotry. "I take responsibility for the party's collapse, but I do not feel guilt. Sharon, with Kadima, entered right into Shinui's niche," Mr Lapid said.