When an isolated Stalinist state led by a hereditary dictator lobs a long-range rocket over your head, it must be difficult to see the bright side. But Taro Aso, the Prime Minister of Japan, has had a good North Korean missile crisis.

Two months ago, he was at the lowest ebb of almost any Japanese leader since the war, and his Liberal Democratic Party seemed doomed to only its second electoral defeat. Today he is back in with a fighting chance, thanks to a combination of luck, shrewd politics, and the helping hand of Kim Jong Il and his intercontinental Taepodong-2 rocket.

There were several good reasons for deploring the rocket launch, but Mr Aso and his government seized upon the poorest of all. The risk of missile technology proliferation and the increased possibility of North Korea being able to launch a nuclear attack – these were the real and reasonable concerns expressed in South Korea, the United States and around the world. Japanese focused on a more personal, but much less likely, danger – that the rocket would break up in mid-flight and fall on their territory.

The rocket's course was to take it over the northern part of Japan, but so far up into the atmosphere that it could be detected only with the most sophisticated military equipment. A previous rocket had exploded and broken up after being launched in 2006, but the chances of this happening again directly over Japan were small. However, in the days leading up to the launch Japan was like a nation waiting for a visit from an angry Godzilla, rather than the passing of a distant and unthreatening space rocket.

Small villages were rigged up with emergency communications systems linked directly to Mr Aso's Cabinet Office. Japan's new and largely untested missile defence shield was activated. So tense were the Japanese Self-Defence Forces that they twice cried wolf, announcing the rocket's launch before it had gone up. But, rather than irritation, the Japanese public appeared grateful to Mr Aso for protecting them from this imagined threat.

Japan took an implacably firm position in the UN Security Council, of which it is at present a non-permanent member. Japanese diplomats claim some credit for the fact that the message of condemnation from the council was a presidential statement, rather than a mere press release - although it fell well short of the legally binding resolution for which Tokyo had been pressing.

This is not the only factor in Mr Aso's bounce from single-digit approval ratings to a much improved 30 per cent this week. He has been helped immeasurably by the misfortunes of Ichiro Ozawa, leader of the opposition Democratic Party of Japan, who had been looking like the prime minister in waiting.

Mr Ozawa's closest aide was arrested and charged with improperly accepting political donations. The scandal seemed ready to envelop Mr Ozawa, but he resisted pressure to resign as party leader. Mr Aso is probably glad that he did – the polls suggest that voters are as disgusted by Mr Ozawa's refusal to go gracefully as they are by the funding allegations, and that for the time being he is a liability to the opposition.

Mr Aso has a further chance to shine when he travels to China to meet President Hu Jintao and the Prime Minister, Wen Jiabao. Those plans were jeopardised when Mr Aso sent an offering to Yasukuni Shrine in Tokyo, where Japan's war dead, including many of those who invaded China, are honoured as Shinto gods. The Chinese expressed their irritation, but the trip is still on.

Mr Aso must feel as if he has returned from the political grave. But the election may be as far off as September and plenty can go wrong before then. As the Japanese saying has it: “In politics, an inch ahead is darkness.”

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