Tokyo Gov. Yuriko Koike declared victory Sunday as exit polls projected her winning a third four-year term as head of Japan’s influential capital.

The vote was also seen as a test for Prime Minister Fumio Kishida's governing party, which supports Koike, the first woman to lead the Tokyo city government.

Tokyo, a city of 13.5 million people with outsized political and cultural power and a budget equaling some nations, is one of Japan’s most influential political posts. A record 55 candidates challenged Koike, and one of the top contenders was also a woman — a liberal-leaning former lawmaker who uses only her first name, Renho, and was backed by opposition parties.

With about 40% of the votes counted, Koike led by more than 1.29 million votes, twice as many as her top rivals Ishimaru and Renho, who had 664,000 and 603,000 votes, respectively. Official results are expected early Monday.

Minutes after exit polls projecting her victory, Koike showed up at her campaign headquarters in Tokyo and celebrated by thanking the voters who chose her.

“I believe the voters gave me a mandate for my accomplishment in the past eight years,” Koike said. She pledged to push for more reforms and support for Tokyo residents.

“I'm fully aware of my heavy responsibility,” she said. “I will tackle my third term with all my body and soul.”

A win by Koike is a relief for Kishida’s conservative governing party, which she has long been affiliated with. Kishida’s Liberal Democratic Party and its junior coalition partner, Komeito, unofficially backed her campaign.

Renho, running as an independent but supported by the main opposition Constitutional Democratic Party of Japan and the Japanese Communist Party, criticized Koike’s ties with Kishida’s party, which has been hit by a widespread slush fund scandal. A victory for Renho would have been a major setback for Kishida’s chances in the party's leadership vote in September.

LDP acting secretary general Tomomi Inada, in an interview with NHK television, welcomed Koike's victory as a “positive development” for the governing party, but stressed the need for the LDP to firmly push its own reforms.

While the two high-profile women gathered national attention, Shinji Ishimaru, a former mayor of Akitakata town in Hiroshima prefecture, was seen to have gained popularity among young voters.

The main issues in the campaign included measures to improve the economy, disaster resilience for Tokyo and low birth numbers. When Japan's national fertility rate fell to a record low 1.2 babies per woman last year, Tokyo's 0.99 rate was the lowest for the country.

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Koike’s policies focused on providing subsidies for married parents expecting babies and those raising children. Renho called for increased support for young people to address their concerns about jobs and financial stability, arguing that would help improve prospects for marrying and having families.

Another focus of attention was a controversial redevelopment of Tokyo's beloved park area, Jingu Gaien, which Koike approved but later faced criticism over its lack of transparency and suspected environmental impact.

Koike, a stylish and media savvy former TV newscaster, was first elected to parliament in 1992 at age 40. She served in a number of key Cabinet posts, including environment and defense ministers, as part of the long-reining Liberal Democratic Party.

Renho, known for voicing sharp questions in parliament, was born to a Japanese mother and Taiwanese father and doesn’t use her family name. A former model and newscaster, she was elected to parliament in 2004 and served as administrative reform minister in the government led by the now-defunct Democratic Party of Japan.