TOKYO — Polls opened Sunday to elect a new Tokyo governor with incumbent Yuriko Koike challenged by opposition stalwart Renho, two prominent women in Japan's male-dominated political sphere.

Japan has never had a woman prime minister and a large majority of lawmakers are men, but Tokyo, accounting for a tenth of the national population and a fifth of the economy, has been governed since 2016 by former television anchor Koike, 71.

While few now tout the former defense and environment minister as a possible future prime minister, as many once did, polls suggest that the media-savvy conservative will win a third straight term in the metropolis of 14 million people.

This will be some relief ahead of national elections due by late 2025 to the ruling Liberal Democratic Party of deeply unpopular Prime Minister Fumio Kishida which backs Koike, even though she broke away from the LDP in 2017.

The election comes after new government data showed the average number of children a woman is expected to have hit a record low of 1.20 last year, and Tokyo's figure was 0.99 — the first below one for any Japanese region.

Both Koike, who has campaigned with an AI-version of herself, and her nearest rival Renho, who goes by one name and is backed by Japan's main opposition parties, have pledged to expand support for child-rearing, with Koike promising subsidized epidurals.

"After having their first child, I hear people say they don't want to experience that pain again," Koike said, according to local media. "I want people to see childbirth and raising children as a happiness, not a risk."

"I will implement genuine long-term fertility measures, support young people thoroughly, and expand their life choices," Renho said. "I will also implement transparent fiscal reforms, where everyone can check the situation."

A dark horse in the race could be independent candidate Shinji Ishimaru, 41, a former mayor of Akitakata in western Japan, recent polls also suggested, with some swing voters preferring him over Koike and Renho.

A record 56 people are standing in the election, not all of them serious, with one dressing as "The Joker" and calling for polygamy to be legalized and others campaigning for more golf, poker or just to advertise their premises in the red-light district.

Local media speculate that the turnout may be higher given that early votes cast through July 5 reached 1.65 million, up 20 percent from 1.38 million in 2020.

Overall turnout was 55 percent in the last vote, down from nearly 60 percent when Koike was first elected in 2016.

Ballot boxes will close at 08:00 pm.