Despite gliding into office as Mr Koizumi's hand-picked successor amid Japan's best economic performance for a decade, the prime minister's approval ratings have dived from the mid-60s last September to 28 per cent, according to several recent surveys. A poll this month by the Asahi newspaper found a record 55 per cent of respondents unhappy with the coalition Liberal Democrat Party/New Komeito government he leads.

Those dismal figures could not have come at a worse time for Mr Abe, 52, who faces his first test with the voters tomorrow. The government must take 64 of the 121 seats up for grabs in the upper house or he may become part of the great pre-Koizumi political tradition of revolving-door prime ministers. Most predictions suggest it has no chance of reaching that target.

'It is now obvious that Mr Abe doesn't have the power to swing this election,' veteran political commentator Hirotaka Futatsuki said.

With stakes like that, it is not surprising that the prime minister is on television most days, jacket off, sleeves rolled up and striking a pose few voters have seen until now - passionate and animated. 'I will not lose,' he bellows from campaign trucks as he fights to remind voters of his achievements.

Those achievements make Mr Abe's brief time in office as momentous and controversial as that of any post-war Japanese leader. In one of the busiest and one-sided legislative campaigns in recent history, his government has radically altered the delicate constitutional balance that has anchored Japan to the world since 1945.

The Self-Defence Forces has been upgraded to the status of a full ministry, and parliament is moving inexorably towards rewriting the 'pacifist' constitution, the first two steps towards the restoration of Japan as a military power. The once sacrosanct 1947 education law has been revised to instil patriotism in young Japanese, and other important changes are on the way.

Mr Abe is proud of his attempt to create what he calls a 'beautiful Japan', which his supporters say has secured his place in history as a radical conservative who finally dragged Japan into the real world.

Unfortunately, most voters care more about bread-and-butter issues than weighty constitutional debate. And with 20 per cent of the population being over 65, few such issues loom larger than pensions.

So there is much unhappiness in the Abe camp that just as their man should be enjoying his moment in the sun, his agenda has been derailed by a pension scandal. Voters are furious that after paying for years into the national pension system, the bureaucrats who run it have lost millions of records.

Panicked by polls suggesting the pension mess is the single biggest election issue for 65 per cent of voters, the government has promised emergency help. But accusations that he was initially slow to act have helped the opposition paint Mr Abe as living in a rarified world far above the mundane concerns of ordinary people.

Given his blue-blood background, those accusations stick. the prime minister's late father, Shintaro Abe, was LDP secretary-general, and his grandfather and political mentor, Nobusuke Kishi, escaped indictment as a war criminal to become prime minister from 1957 to 1960.

Sponsored by the back-room brokers who run the LDP's factions, particularly former prime minister Yoshio Mori, Mr Abe has 'led a charmed political life', says Takao Toshikawa, editor of the political magazine Tokyo Insideline. 'This is his first real test.'

Mr Abe came into office nursing twin policy obsessions: rewriting the 1947 constitution and reforming the education system, both of which have been on the LDP wish list since 1955. His grandfather also tried but failed to revise the constitution in the teeth of opposition from socialists and pacifists.

Mr Abe has in his own mind reversed that family stain, but there is little evidence that his intensely ideological programme has been popular with voters.

'The key issues of his government had nothing to do with ordinary people,' said Jiro Yamaguchi, a professor of politics at Hokkaido University.

A string of support-sapping scandals on his watch have added to the public perception of a man out of his depth.

Just as he thought he had ridden out the May suicide of Toshikatsu Matsuoka during a corruption investigation, the late agriculture minister's successor, Norihiko Akagi, is also being accused of padding expenses.

Commentators have noted that Mr Abe has refused to sack any of his errant ministers, including health chief Hakuo Yanagisawa, who called women 'baby-making machines'. Defence minister Fumio Kyuma stepped down this month after defending the US atomic bombings of Hiroshima and Nagasaki.

'The impression is that he can't control his ministers,' Mr Toshikawa said.

The latest polls show the ruling coalition struggling at least eight percentage points behind the Democratic Party of Japan (DPJ), led by political veteran Ichiro Ozawa. Doomsday scenarios suggest the LDP may match its worst ever upper house performance in 1989, when it won just 36 seats.

A big loss could stall Mr Abe's legislative agenda, which needs both houses of parliament onside if it is to succeed. He could soldier on, but the odds are against it: His predecessors both resigned after similar electoral beatings in 1989 and 1998.

The LDP is unlikely to tolerate a lame-duck leader for long, even one with such an impeccable pedigree.

If Mr Abe goes, and it probably will not be until at least the autumn, the hot money is on Foreign Minister Taro Aso to step into his shoes. Mr Aso, who is also the scion of a prominent political family, was a runner-up in last autumn's leadership election, although his right-wing politics, often-tactless language and allegations that his family's wartime mining business used slave labour will hardly endear him to Beijing or Seoul.

Of course, Mr Abe may somehow survive, but it will be an uphill battle. For a man who has never had to struggle very hard for anything, tomorrow may prove to be the fight of his life.

'It is now obvious that Mr Abe doesn't have the power to swing this election

Hirotaka Futatsuki, political commentator