BBC News' Jeremy Bowen reports on a serious blow for Mr Netanyahu

On Sunday afternoon the third of three trailing candidates, right-winger Benny Begin, pulled out of the race.

His announcement came only hours after the withdrawal of former Defence Minister Yitzhak Mordechai.

At a hastily-called news conference in Tel Aviv, Mr Mordechai offered qualified backing for the opposition Labour Party candidate, Mr Barak.

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"We must change the government in Israel and I think that Ehud Barak has the qualities and experieces needed to be prime minister, even though I know his limits," Mr Mordechai said.

Mr Begin did not endorse either of the remaining candidates, but instead blamed the "change of circumstances in the past few hours" for his withdrawal.

Mr Barak has led Mr Netanyahu by between 6% and 13% in final week opinion polls, but until the withdrawal of Mr Mordechai and Arab candidate Azmi Bishara, he could not have expected the 50% needed to win a first round.

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It is not thought that the withdrawal of Mr Begin will be as significant as those of Mr Mordechai and Mr Bishara.

His opinion poll rating was around 2% and it is not clear whether his supporters will transfer their votes to Mr Netanyahu.

Barak riding high

Mr Barak denied suggestions that the candidates who pulled out had done any deals with Labour.

Instead he painted a picture of the country turning against Prime Minister Netanyahu.

"In the last days, Israel is uniting in order to bring about a change and hope," he said at an open-air meeting.

"I am calling on all of Israel, to all those who believe in uniting the country ... to come with me," he said.

Netanyahu hits back

Prime Minister Netanyahu brushed aside implications of other candidates withdrawing on the eve of elections.

But he accused Azmi Bishara of "clearly co-ordinating" his withdrawal with Mr Barak.

Mr Netanyahu said this meant Mr Barak intended to allow the establishment of a Palestinian state "on the outskirts of Tel Aviv".

And he accused Mr Mordechai of losing his credibility by standing aside for the Labour leader, and he called him an ex-general who was threatening Israeli security.

Minutes after the Mordechai withdrawal, Mr Netanyahu appealed to dissidents to "come home".

"Come home to Likud, it's your true home," he said in a televised news conference minutes after Mr Mordechai's withdrawal.

Mordechai's flop

Electoral support for Mr Mordechai plunged in the polls since he formed the Centre Party with other dissidents from Likud.

Bishara withdrew to help defeat Netanyahu

He was sacked from Mr Netanyahu's cabinet for "putting personal ambition first" as the prime minister called it.

His candidacy in the elections for the premiership was explicitly aimed at ousting Mr Netanyahu and he expressed confidence he could do it.

He comes from Israel's small community of Kurdish Jews, but his supporters said he would appeal to the large constituency of Jews hailing from Middle Eastern countries.

Many Sephardim, as they are called, are dissatisfied with the Israeli political establishment, who predominantly have their origins in Europe.