There is little doubt in Israel that Netanyahu's conservative Likud, running jointly with former foreign minister Avigdor Lieberman's nationalist Yisrael Beitenu, will win the highest number of parliamentary seats in the coming ballot.

But surveys show the Bayit Yehudi party headed by Naftali Bennett, a high-tech millionaire and former Jewish settler leader who wants to annex parts of the occupied West Bank, steadily chipping away at Netanyahu's margin.

One poll last week showed Bennett coming in second in the vote after drawing support from Netanyahu's traditional power base.

"I believe there is only one way to ensure the right remains in power in Israel, and that is to vote for me, for the joint Likud-Yisrael Beitenu list (of parliamentary candidates)," Netanyahu told Israel Radio.

"Any other vote, by those who want me as prime minister and don't vote for me, increases the chance that the left will return to govern and lead the country instead of us."

Bennett's showing in the opinion polls has driven the first chink in Netanyahu's armour in an election widely viewed as an affirmation of the prime minister's leadership of Israel rather than a real challenge to his stewardship.

No one party has ever won a parliamentary majority in an Israeli election. A strong result for Bennett could improve his prospects for a top position in a Netanyahu-led coalition and raise more international concern about settlement policy.

Peace talks with Palestinians seeking a state in territory Israel captured in a 1967 war have been frozen since 2010, and Jewish settlement has been expanding in the West Bank.

Flanked on the right by Bennett, Netanyahu faces a further challenge from Israel's centrist and left-wing parties, circling with renewed vigour after smelling a trace of blood in the political waters.

On Saturday, former foreign minister Tzipi Livni, head of the centrist Hatenuah party, said she and leaders of the centrist Yesh Atid and left-leaning Labour parties would "discuss the creation of a 'united front' to work together to replace Netanyahu".

Opinion polls suggest the three parties could collectively win about 37 parliamentary seats two more than the number projected for Likud-Yisrael Beitenu and potentially be tasked by Israeli President Shimon Peres with forming a government.

But disagreements over the terms for any centre-left partnership could make it elusive.

Center>Copyright Reuters, 2013