First would-be female PM marks shift in Japan

Takako Doi led the Socialist Party from 1986, and helped the opposition win a historic upper house election victory in 1989, but she stepped down in 1991. In 1993, she was appointed the first female speaker of the lower house.

A second stint as party leader was less successful, and the remnant of her party is now only a minor player.

But even feminists who welcome the advent of a woman candidate for prime minister express doubt about whether Koike, a former environment minister who has served as a national security adviser and briefly as defence minister, is the right choice.

"She is the first woman to stand for the party leadership and I would like to congratulate her on that," said Mitsuko Yamaguchi, chief executive of the Fusae Ichikawa Memorial Centre, which promotes women's involvement in politics.

"The problem is what kind of policies she can come up with," Yamaguchi said. "She didn't come up through economic policy.

"There are many problems in this election, from huge public debt to the slowing economy and the ageing population. What to do about the economy is an extremely important issue. Other candidates are specialists in the economy."

(Additional reporting by Naoto Okamura and Linda Sieg; Editing by Chris Gallagher)