A local Tokyo assemblyman could become Japan's first openly gay male lawmaker if he wins a seat in next month’s general election.

Taiga Ishikawa, 40, who failed in his bid to become leader of the Social Democratic Party last year, will be ranked at the top of the small opposition party's proportional representation list in Tokyo. That puts him in pole position among the party's candidates to win a seat in parliament.

Mr. Ishikawa told Japan Real Time that he is eager to promote the legalization of same-sex marriage, environmental conservation, women’s rights and support for the disabled if he is successful in his bid to enter politics at the national level.

"My goal is to promote diversity in the community,” Mr. Ishikawa said.

He added that his decision to run in the election was partly inspired by public figures that have recently come out, including Apple Inc. chief executive Tim Cook and Australian swimmer Ian Thorpe.