Israel's notoriously turbulent political climate could become even stormier after members of the ruling Kadima party cast their ballots tomorrow to select a new leader.

Depending on a welter of variables, the winner in tomorrow's party primary might ? or might not ? become the country's new prime minister.

If the winner does become prime minister, he ? or she ? would replace the outgoing Ehud Olmert, who has been brought low by a series of financial scandals.

But events could play out in a variety of different ways and, right now, no one knows which of them is most likely.

"It's a crazy situation, no question," said Emanuel Gutmann, emeritus professor of political science at Jerusalem's Hebrew University.

The campaign leading to the vote has been typically boisterous. This is Israel, after all, where politics are practised without the benefit of gloves.

But the real rough-and-tumble may begin only after the results are known. More than 70,000 people are eligible to mark their ballots in the poll.

The contest seems to have narrowed to a two-person race, pitting Foreign Minister Tzipi Livni, 50, against Transportation Minister Shaul Mofaz, 60, who is a charter member of the network of former army officers that has traditionally run this country's affairs.

Mofaz previously served as the Israel Defense Forces' chief of staff and later as the country's defence minister.

Livni has generally been considered the favourite to win, but many analysts say the race is too close ? or too unpredictable ? to call.

The campaign has been marred by allegations of improper attempts to manipulate the voter rolls or the voters themselves, attempts observers say will likely favour Mofaz.

Public Security Minister Avi Dichter and Interior Minister Meir Sheetrit are also in the race but are widely judged to be lagging well behind the two front-runners.

Issues of personality, more than policy, have dominated the campaign, but analysts consider the vote's outcome to be important nonetheless, both for Israel and the region. The results could go a long way toward squelching ongoing peace talks between Israel and the Palestinians, if Mofaz triumphs, or else help keep an already troubled process somehow shuffling forward, should Livni prevail.

But first, the new Kadima leader would have to battle for the job of prime minister, either by keeping together a fragile four-party coalition that currently exerts a slender grip on power or by fashioning a new arrangement of parties that could claim a majority of seats in the 120-seat Knesset or parliament.

Neither of those prospects is guaranteed. If no government can be formed through negotiations among the parties, new general elections would have to be held, probably sometime next spring, and no one can say what fresh uncertainties that would bring.

In the event of a new vote, Olmert would probably be obliged to carry on as caretaker prime minister ? and lamest of Middle Eastern ducks ? assuming he is not indicted on corruption charges before a new poll could be held.

"The entire thing is a mess," said Tamar Hermann, director of the Tami Steinmetz Centre for Peace Research at Tel Aviv University and a respected Israeli pollster.

But the messiness of the situation has not prevented some contestants in tomorrow's vote from issuing self-assured predictions, as if the race were unfolding in a state of perfect order.

On Sunday, Mofaz predicted he would win with 43.7 per cent of the vote ? a claim dismissed by the Livni camp and one that left Hermann shaking her head.

"There is no way of having a representative sample of Kadima voters," she said. "Each side is using pseudo-scientific data, which is totally unreliable. It's pure speculation."

Kadima, which means "forward" in Hebrew, was formed in 2005, largely as a personal political vehicle for then prime minister and Likud party leader Ariel Sharon, in order to carry out his plans for the unilateral withdrawal of Israeli settlements from Palestinian territories. In January 2006, however, Sharon suffered an incapacitating stroke, and Kadima was left to find its way without its founding spirit.

A former member of the right-wing Likud party, Livni was a Sharon prot?g? who migrated to Kadima when it was first set up.

According to Hermann, Livni is popular among women, centrists, leftists, the affluent, and the well-educated, while Mofaz resonates more powerfully with those she called "simple folk."

If successful, Livni would be Israel's first female prime minister since Golda Meir more than three decades ago.