JERUSALEM - Members of Israel's ruling party vote on Wednesday for a new leader to replace Prime Minister Ehud Olmert, who has promised to resign following a corruption investigation in which he faces indictment.

But whether Tzipi Livni or fellow cabinet minister Shaul Mofaz secures the support of a majority of the 74,000 members of the centrist Kadima party, Olmert may stay on as caretaker premier for weeks or months -- and Israel's fractious coalition politics could yet mean an early parliamentary election.

After what many had thought might be his last such meeting with Palestinian President Mahmoud Abbas on Tuesday, Olmert vowed to carry on with their peace negotiations -- a sign he aims to exercise his right to continue as prime minister while his successor as party leader tries to form a new government.

Polls show Foreign Minister Livni well ahead of Mofaz, the transport minister and a former general, in her bid to become Israel's first woman leader since Golda Meir in the 1970s.

But both camps remain cautious, citing the patchy record of surveys in such contests. A poll on Monday showed Livni with 47 percent to Mofaz's 28 percent, with the two other candidates trailing. But Mofaz has predicted he will win, and secure more than the 40 percent needed to avoid a runoff vote next week.

Whoever succeeds Olmert, many see a parliamentary election in months. Kadima, founded in 2005 by Ariel Sharon, has just a quarter of the seats in the Knesset. Rivals, some within Olmert's coalition, are preparing for a national battle that polls show may favour Benjamin Netanyahu's right-wing Likud.

Livni, who is Israel's chief negotiator in the peace talks launched by U.S. President George W. Bush 10 months ago, is widely seen as offering continuity in that process -- but few on either side see a major breakthrough for peace before Bush himself leaves office four months from now.

Mofaz, as army chief and then defence minister, garnered a reputation for tough tactics against a Palestinian uprising from 2000. He has also said an attack on his native Iran could become "inevitable" if it pursued a programme to develop nuclear arms.

The Israeli public has found it hard to muster enthusiasm for the Kadima primary, though its portrayal in some quarters as a showdown across Israel's perennial divide between Jews of European and Middle Eastern descent has enlivened debate.

Mofaz, 59, who migrated from Tehran as a child in the 1950s, would be the first prime minister not of European origin.

Many of his fellow Sephardic Jews complain of feeling second-class citizens to Ashkenazis from Europe. Livni, a 50-year-old lawyer and former Mossad intelligence agent, is the daughter of a famed Polish-born guerrilla fighter of the 1940s.