Israel's main opposition Kadima party on Tuesday elected Shaul Mofaz as their new leader in place of Tzipi Livni, preliminary results showed early Wednesday.
According to an initial sampling of 127 of the 197 ballot boxes, Mofaz had secured some 65 percent of the vote, compared with Livni's 35 percent, Israel's main television and radio stations reported.
Turnout among the party's 95,000 voters, who began casting their ballots at 10:00 am (0800 GMT) on Tuesday, was 45 percent.
Pundits had predicted a very tight race between Livni and her deputy, but the preliminary results showed Mofaz taking a decisive lead.
Kadima is currently the largest party in parliament, holding 28 seats in the 120-seat Knesset, but a series of recent polls suggest the faction is likely to see that number halved in the next elections.
Those elections are officially tabled for October 2013, but rumours of an early election are rife, with observers speculating they could take place before the end of this year.
Tuesday's primary vote pitted Livni, Kadima's current leader and former foreign minister, against her deputy Mofaz, an Iranian-born former army chief-of-staff who once held the defence portfolio.
Both are former members of the now-ruling right-wing Likud party of Israeli Prime Minister Benjamin Netanyahu.
The two have been bitter rivals since they fought a very tight leadership race during the last primaries in September 2008 which saw Livni winning the vote by just 413 votes and replacing scandal-plagued premier Ehud Olmert as party head.
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Despite his rich history of military experience, Mofaz has spent only 10 years in politics, although he currently heads the powerful parliamentary committee on foreign affairs and defence.
Speaking to reporters as he cast his vote earlier on Tuesday, the 63-year-old said he was ready to take on Netanyahu.
"The Kadima primaries are a vote on the future, on the character and the values of the state of Israel," he said.
"At the end of this day, Kadima will set out on a new path as an alternative to the poor government of Netanyahu. I intend to win at the general elections and to replace Netanyahu."
Kadima was founded in November 2005 by former prime minister Ariel Sharon who took leave of his political home in Likud after his controversial decision to pull all settlers and troops out of the Gaza Strip.
It has since grown to become Israel's largest party, but has taken a hammering in the polls over what commentators say has been a failure to present a concrete alternative to Netanyahu and his right-wing coalition.
While most Israeli commentators were unsure who would win the race, they were unanimous that the primary vote was likely to mark the end of Kadima as Israel's biggest party, saying the outcome would see it split apart.
"For some time Kadima has not been an alternative to the government. According to the polls, its public standing -- whether headed by Livni or by Mofaz -- is at a nadir," wrote commentator Sima Kadmon in the top-selling Yediot Aharonot.
"It is the largest party in the Knesset, and it has zero influence," she said, noting that whoever takes the helm will have to try and restore Kadima to its former standing.
"With Livni or with Mofaz, it is highly doubtful that that is possible."