The date of the September 12 Labor Party primary was chosen unintentionally, but it could not be more symbolic. The party that towered over the country it ran for nearly three decades before it was felled by poor leadership and unrestrained infighting will begin the process of rebuilding itself under a new leader.Unless none of the four candidates obtains the 40 percent of the vote necessary to avoid a September 21 run-off race, Monday could mark the beginning of the resurrection of the party whose forerunner reached a peak of 56 mandates in the 1969 election and was left with a nadir of eight following its January 17 split.The new leader will face the challenging task of uniting a party divided by the election, bankrupted by years of overspending, and burdened by its bad image and the unmeetable expectations of its storied history.Labor has been leaderless since Ehud Barak and four of his allies left to form the new Independence Party. The divorce has been helpful to Barak, who enabled himself to remain defense minister, and to Labor, which immediately received an influx of young members who were turned off by Barak and his perceived hedonism.A party that until recently was seen as a veritable nursing home looked young and vibrant at Wednesday night’s convention at Beit Berl Teachers College in Kfar Saba. Young activists in T-shirts bearing the candidates’ slogans stood up throughout the raucous forum in the packed auditorium, which was covered with confetti.While Barak headed Labor, there were no discussions about the party’s ideology. Its platform hasn’t been written since Binyamin Ben-Eliezer led the party a decade ago, and its positions on key issues have been unclear for many years.Whoever wins will infuse the party with their spirit and their ideology. All four candidates would put more of an emphasis on socioeconomic issues, seeking to take political advantage of the protests over the high cost of living.MKs Shelly Yacimovich, Amir Peretz and Isaac Herzog, and former chairman Amram Mitzna all have extensive social affairs experience on their resumés.One of the keys to their success will be whether they can become the political voice of the protesters or whether they will leave the task to future parties likely to be formed by journalist Yair Lapid and former Shas leader Arye Deri.BUT BEFORE any of the candidates can start thinking about the next general election, they have to face a primary election that can still go in any one of three directions.The best-case scenario for the party is that one of the candidates obtains the necessary 40% to win outright on Monday. Labor would save the expenditures of another day of voting and be spared the negative attention a divisive, head-to-head race could bring.The most likely scenario, however, is that Yacimovich will face off against Peretz, her political-mentor- turned-adversary, in a nine-day race that could be nasty. The bad blood between the two may not result in a second split in the party, but it could leave the victor permanently scarred and make his or her job of uniting the party even harder.The third possibility is that between now and Sunday night, Mitzna will give in to tremendous pressure to quit the race and follow the lead of venture capitalist Erel Margalit, who exited the contest and endorsed Herzog on Wednesday.Several current and former Labor officials are expected to warn Mitzna over the weekend that his insistence on remaining in a race that he cannot win could result in him crowning Yacimovich, whom he slammed in a sparsely attended Jerusalem parlor meeting this week.He blasted her for having nothing to say on key issues like diplomacy, security, education, and the separation of religion and state. He belittled support for her as “trendy” and compared her to the Pensioners Party, which won seven seats as a political fad.“Her record in the Knesset is impressive, but chairman of the party?” Mitzna asked. “Has she in her life managed more than two people? If you have a business, do you want the person who runs it to be someone who has run something in the past? If you have a fancy car, would you trust it to someone who has never driven before?” Mitzna said that Yacimovich “has a problem working as a team,” and mocked the age of the MK, who at 51 is 15 years his junior.“Little by little,” he said. “You are a young lady. You still have time.”Mitzna resisted three weeks of pressure to back Herzog, and his speech to the convention was especially defiant, leading Labor officials to believe he will stay in the race until his bitter end and quit politics as a tragic figure with unmet prime ministerial potential.On a visit to Yeroham in December, Labor’s elder statesman Ben- Eliezer urged Mitzna to run, and even said that “only Mitzna can save the party.” But since then, Ben- Eliezer has maintained neutrality, and he never gave Mitzna the boost that he needed to win.One Labor official described Mitzna as suffering from the trauma of his decisions to quit the Labor leadership and then the Knesset. The official said the former general wanted to go down as a fighter and not be remembered as a serial quitter.Another explanation is that Mitzna believes that endorsing a candidate would harm his chances of latching on with another party ahead of the next election. It is possible that he would rather be Lapid’s No. 2 than Yacimovich’s.If Mitzna surprises and leaves the race on Sunday, Herzog would receive a boost that could propel him to a second round of voting against either Yacimovich or Peretz.Since he lacks the political foes that the two of them have, Herzog could unite Labor’s leadership against either of them and win.No matter which of the three scenarios plays out, eight months of political purgatory for the Labor Party will end this month, and its rebuilding will begin. The test that will determine whether the new leader can succeed will be whether he or she can unify Labor the way America banded together the day after September 11 a decade ago.