For the first time, there are over 100 million eligible voters in greying Japan. And according to opinion polls, about 35 million of them have not yet decided which way to vote in elections for the powerful lower house of the Diet this Sunday.

This is bad news for the dominant force in Japan's ruling coalition, the Liberal Democratic Party, which in recent elections has failed to attract the floating vote.

In 1998, upper house pre-election opinion polls indicated that the LDP, which has been in effective power for all but about two of the last 45 years, was headed for a sweeping victory. Instead, the electorate gave the party a bloody nose, forcing the leader, Ryutaro Hashimoto, to resign following a humiliating defeat in which the party failed to secure a single seat in either Tokyo or Osaka.

Since then the LDP has been particularly distrustful of opinion polls. Hence the honest, if ill-advised, comment of the Prime Minister, Yoshiro Mori, during a speech on Tuesday that, for the undecided voters, "it would be all right if they just slept on that [election] day".

Superficially, there appear no significant grounds for the LDP to be uneasy about the election. Though its coalition allies, the Komei party and the New Conservative Party, are likely to see big losses, opinion polls in Japan's leading dailies published in the last few days indicate almost uniformly that the ruling parties will together win a solid majority of the 480 lower-house seats and continue in power.

For the three parties, a joint total of 254 seats would represent victory. Though a substantial fall from the 331 seats which they currently possess, the magic number of 254 would allow them to appoint the heads of all parliamentary committees as well as secure a solid majority.

But the increasing influence of unaffiliated voters, who have in recent years elected unaligned politicians in Japan's biggest two cities, Tokyo and Osaka, is the loose cannon that may prove the undoing of the government.

Analysts say the floating voter will use the poll partly to deliver a verdict on Mr Mori's leadership. A one-time journalist, Mr Mori is a controversial figure. In his political past he has been linked to a number of scandals, including the Recruit shares-for-favours scandal that brought down the government in 1989.

A former member of the strongly nationalist right Seirankai, a now defunct LDP group, he has provoked strong criticism recently for using phrases which invoke images of pre-war militarism.

There was public outrage when Mr Mori told a group of pro-Shinto politicians last month that Japan was "a divine nation centring on the emperor".

The words he used, which mirrored the lyrics of a militaristic song learned by schoolchildren during the second World War, sent Mori's ratings in deeply pacifist Japan plummeting.

The rapidity of his slump in popularity became something of a joke. One noodle-shop owner in Gifu Prefecture, an LDP stronghold, began tying the price of a noodle dish to Mori's ratings, a highly unprofitable move as those ratings sank below 15 per cent.

Though the Prime Minister's standing has slightly improved of late, the opposition has fought the election campaign in large measure on what it sees as Mr Mori's unfitness to hold office.

This strategy may not dramatically affect the LDP because Mr Mori's unpopularity doesn't necessarily translate into unpopularity for the party, whose ratings remain in the 3540 per cent range.

Of perhaps more pressing concern for voters is how to fix a stagnant economy that needed massive doses of public funds to record a 0.5 per cent growth for 1999 after languishing for two years in minus territory. Pump-priming measures have sent the national debt soaring. In the current fiscal year it will exceed 645 trillion yen, or 129 per cent of gross domestic product, a level of indebtedness unequalled among the world's major industrial nations.

The LDP-led coalition has promised to continue with the pumppriming until the economy reaches 2 per cent growth. Yukio Hatoyama, leader of the main opposition Democrat Party of Japan, calls this policy reckless.

A former LDP member, who comes from a long-established political family known as "the Kennedys of Japan" and leads a party that is home to a mixed bag of members with different ideologies, Mr Hatoyama proposes increasing the tax burden of the lower-paid and tightening public spending.

Since the election campaign began, his enthusiasm for fiscal rectitude at the expense of wage-earners has been harshly criticised, forcing him to slightly revise the scheme.

Questioning its appropriateness so soon after the economy has begun to show signs of revival, the LDP secretary-general, Hiromu Nonaka, described the plan in a televised political debate as "the same as forcing a person just recovered from illness to run naked".

The LDP has also tried scare tactics with conservative voters who may think of supporting the Democrats, by loudly broadcasting that the Democrats may enter into government with the Japanese Communist Party. The Democrats deny that any alliance is in the offing, and such an arrangement would be a bitter pill for the strongly anticommunist Hatoyama to swallow.

But the creation of a broad coalition including the communists, who are decidedly euro-communist in orientation, may yet present itself as the only option to keep the LDP out of power, according to some commentators.

The communists are the second-largest opposition party, with 26 seats. They did surprisingly well in the last upper-house elections, winning over eight million votes and, with the ability to mobilise election workers from its some 370,000 members, the party may provide another surprise.

The leader of the communists, Tetsuzo Fuwa, has also recently softened the party's line calling for the abolition of the Japan-US security treaty, making the party more acceptable to possible moderate coalition partners.

But crucial to the equation are those 35 million voters that Mr Mori said he would prefer stayed in their beds. According to Mr Hatoyama, a 60 per cent turnout, about the same as that for the last lower-house election in 1996, would give the LDP opposition a landslide win, but a 70 per cent turnout would swing things in favour of the Democrats, opening up the possibility of a non-LDP government.

A survey by the influential business daily Nihon Keizai Shimbun showed that almost 90 per cent of those who are eligible plan to vote. But according to a Japanese-American commentator, Glen Fukushima, writing in the Japan Times, the weather may well decide the outcome. Simply put, nice weather will boost turnout and that could prove a disaster for the LDP. But the party may not have to worry. Most of the country is currently experiencing the rainy season the forecast for Sunday is not good.