The battle to become the next Prime Minister of Japan has narrowed into a confrontation between an unpredictable right-winger with a penchant for comic books and a colourless and austere moderate who admits the contest has left him “flustered”.

Today, the second of these men, Yasuo Fukuda, was surging ahead of his rival, Taro Aso, who had appeared to be in an unbeatable position yesterday. The reversal reflects the alarm and uncertainty that has gripped the ruling Liberal Democratic Party (LDP), ever since the current Prime Minister, Shinzo Abe, announced his decision to resign three days ago.

The two candidates are in opposite ideological corners of the LDP, whose control of the lower house of Japan’s Diet gives it the power to choose the Prime Minister. Mr Aso, 66, the secretary-general of the party and former Foreign Minister, is a conservative and nationalist who favours a close alliance with the United States and has offended minority groups, as well as Japan’s Asian neighbours, with his outspoken opinions.

By contrast, Mr Fukuda, 71, favours greater engagement with Asia and opposes visits to the controversial Yasukuni war shrine. As Japan’s Chief Cabinet Secretary, he earned a reputation for caution and reliability but he is dry and restrained to the point of being boring, and has none of the populist passion of his opponent.

“I never even dreamt I would find myself in such a position; it’s something I hadn’t considered at all,” Mr Fukuda told a meeting of MPs today. “I am rather flustered . . . This is an emergency situation so I will do what I must do. I have a strong sense that I should do this for the country to move Japanese politics forward.”

Since the beginning of the new millennium, Japanese politics has taken a distinct lurch to the right, with conservative nationalists more prominent and powerful than at any time since the Second World War. In different ways Mr Abe, his predecessor and mentor, Junichiro Koizumi, and Mr Aso have led this shift.

Mr Koizumi radically reformed Japanese politics but his pilgrimages to the Yasukuni shrine, where Class A war criminals are honoured, enraged and alienated China and South Korea. Mr Abe chose not to pray at Yasukuni and mended relations with the neighbours but his introduction of “patriotic education”, his ambiguous remarks about Japanese wartime atrocities, and his plans to revise the country’s postwar pacifist constitution marked him out as an ideological conservative.

If anything, Mr Aso is more outspoken and provocative than both of them. Over the years he has upset Koreans by suggesting that they benefited from Japanese colonial rule, offended members of Japan’s untouchable class by declaring that they are unfit for political office and alienated ethnic minorities by describing the country as “one civilisation, one language, one culture, one race”.

He believes that not only Japanese politicians, but even Emperor Akihito should visit Yasukuni shrine, a step which would devastate relations between the two countries. “The more China voices [opposition], the more one feels like going there,” he said last year. “It’s just like when you’re told ‘Don’t smoke cigarettes’, it actually makes you want to smoke. It’s best [for China] to keep quiet.”

His croaky drawl and lordly demeanour make him instantly recognisable. He is a passionate fan of manga comic books and animation; as Foreign Minister, he established an international prize for cartoonists. After Mr Abe’s resignation on Wednesday, shares in manga-related companies rose sharply in anticipation of a comic boom under an Aso administration.

Mr Fukuda belongs to the wing of the LDP which seeks to balance Japan’s military alliance with the US with close and sensitive dealings with China. At 71, he is the choice of the older generation of LDP politicians who feared that they had been passed over by the succession of Mr Abe, a relative junior at 52.

Last night Mr Fukuda had secured the support of the biggest and most powerful factions in the LDP. The only thing that could save Mr Aso now is a revolt in the LDP's prefectural branches, who command 141 votes compared to 387 cast by Diet members.

In July the party lost control of less powerful upper house of the Diet to the opposition Democratic Party of Japan. It faces the real prospect of being forced into a general election in which it could lose power for only the second time in 52 years.

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