Gov. Yuriko Koike’s upstart Tomin First party scored a sweeping victory Sunday in the Tokyo Metropolitan Assembly election, dethroning the Liberal Democratic Party and damaging Shinzo Abe’s prospects for winning another term as prime minister.

With 49 seats, Koike’s Tomin First no Kai (Tokyoites First) became the largest party in the 127-seat assembly.

“The result is much better than we had expected,” Koike said in an interview on Fuji TV. “Our candidates are all fresh, and this new lineup will make the assembly something completely different.”

In the final results, the LDP and Komeito each captured 23. The polls closed at 8 p.m.

History shows the outcome of the assembly election often sways the direction of national politics. The LDP’s historic fall from power in August 2009, for example, was preceded by the Tokyo chapter’s crushing defeat in the assembly election just 1½ months before.

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Hakubun Shimomura, head of the LDP’s Tokyo chapter, acknowledged the party’s scandals at the national level had taken a severe toll.

“This is a very harsh result. What happened in national politics has evolved into a huge backlash against us. I feel very responsible,” Shimomura was quoted by Kyodo News as saying.

With only 23 seats, the LDP fell well below its record low of 38 seats in the 2009 assembly election.

Koike’s commanding victory immediately sparked alarmist accusations that Tokyo would turn into a “Koike kingdom” where the governor and her team would dominate all the decision-making processes in the capital.

Koike said this won’t be an issue.

“The new metro government will be much more transparent and afford Tokyo residents a greater opportunity than ever to monitor what we do,” she told Fuji TV.

All eyes are now on Koike. The former senior LDP lawmaker and Cabinet member could lead Tomin First into national politics and become a potential threat to Abe’s LDP, which has remained unchallenged since he took office in 2012.Voter turnout was 32.36 percent as of 6 p.m., up 2.83 points from the previous election. The election committee said early voting had surged 1.5-fold to 1,355,163.

Sunday’s quadrennial election was effectively a showdown between Koike’s fledgling party and Abe’s LDP, which had dominated the 127-member assembly with 57 seats, followed by Komeito with 22 and the Japanese Communist Party with 17.

Tomin First, which held only six seats before the race, fielded 50 candidates for the election, including a lawyer, a doctor, a journalist and an entrepreneur.

Throughout the campaign, Koike accused the LDP of being the bastion of establishment politics, saying corruption, vested interests and opacity had crippled the legislature of the city of 11 million people.

Koike also got help from Komeito, the LDP’s junior partner in Abe’s ruling coalition, after it severed its longtime partnership with the LDP in the assembly last year when the LDP balked at the idea of slashing assembly members’ salaries. The LDP and Komeito remain partners at the national level, however.

“We can’t revolutionize Tokyo unless we rejuvenate this very, very old metropolitan assembly,” Koike said in a video message Saturday.

In particular, Tomin First has pledged to reduce wasteful spending, eliminate special privileges bestowed on assembly members and disclose more information on the policymaking process of the metropolitan government. It has also advocated the enactment of an ordinance to crack down on smoking in public locations, a controversial topic as Tokyo, a smoking haven, prepares to host the 2020 Olympics and Paralympics.

As he addressed a crowd Friday in the city of Koganei in western Tokyo, Abe emphasized the LDP’s credentials and reliability, obliquely criticizing Koike for trying to destabilize city politics by pursuing drastic change.

“The question should not be whether the assembly is new or old, but whether it is competent or incompetent,” Abe said, claiming the LDP had the ability to boost the economy, reduce overwork and resolve the day care shortage in the capital.

Abe likened Tomin First to the now-defunct Nihon Shinto (Japan New Party), which rocketed to stardom on vows to shake up the establishment in the 1993 assembly election, only to disband a few years later and “usher in political instability,” he said. Koike served as deputy head of that party.

It remains to be seen how much longer Tomin First can maintain its momentum, which is largely dependent on Koike’s popularity. Although Koike won last year’s gubernatorial election by a landslide, recent polls show her support rate is on the decline, sinking from 74 percent in April to 59 percent last week, according to the daily Asahi Shimbun.

Koike has come under fire for what critics call her “indecisive” handling of thethe Tsukiji relocation plan, which will see move to a pollution-tainted site in the Toyosu district. She finalized the plan last month.

Koike said during her election campaign for the governorship last year she had suspended plans for the relocation. And after she was elected governor, she said it would be put on hold for further investigation. Sunday’s election, as it turned out, not only focused on issues inherent to Tokyo, but also evolved into something of a referendum on Abe’s politics, which have been tainted by a string of scandals in recent months.

“We believe the status quo of the Abe administration should be scrutinized as much as possible in this metropolitan election — including its refusals to explain, investigate and reopen the Diet,” Renho, president of the main opposition Democratic Party, told reporters last month.

She was blasting Abe for what she calls a lack of accountability for the so-called Kake Gakuen scandal, in which Abe’s team allegedly gave preferential treatment to a school run by his longtime friend, Kotaro Kake, to help facilitate the opening of a new veterinary department in Ehime Prefecture.

Cascading revelations of alleged favoritism, coupled with the ruling coalition’s railroading of a contentious conspiracy bill through the Diet, have taken a heavy toll on his Cabinet’s support rate, as was shown by opinion polls last month.

Public outcry escalated last week when Defense Minister Tomomi Inada hit the campaign trail Tuesday and claimed the Self-Defense Forces was backing an LDP-endorsed candidate running for the Tokyo election, a comment that took the shine off pacifist Japan’s postwar efforts to keep the military out of politics.

Audio files purportedly having the sounds of LDP lawmaker Mayuko Toyota ranting hysterically — and sometimes even hitting — at her male secretary also went viral.

The groundswell of public discontent apparently put Abe on the defensive, with the leader opting to deliver most of his campaign speeches indoors, such as at an elementary school gymnasium, to minimize his exposure to jeers from onlookers.

But on Saturday, Abe finally hit the streets, addressing a crowd at JR Akihabara Station to drum up support for an LDP-backed candidate vying for the seat in Chiyoda Ward.

A throng of booing anti-Abe protesters lurched forward as he appeared, giving the prime minister, who doubles as LDP president, the middle finger and chanting “Go home!” and “Step down!” while he spoke.

Abe, who in previous speeches repeatedly apologized to LDP supporters for his failure to contain his anger during this past Diet session, fired back at the protesters, saying the LDP “would never stoop to disrupting somebody’s speech with insults.”

“We can’t let those people have their way!” he said, pointing at the protesters.

Also at issue is the fate of the struggling DP, the main opposition force, which pundits estimated was headed for a crushing defeat in the Tokyo election and may even find itself on the verge of dissolution.

The party had seven seats in the assembly before the election, and a loss will further weaken its standing in national politics, potentially igniting calls for Renho’s resignation and prompting some of its lawmakers to bolt and form a new party.

Ahead of Sunday’s poll, Renho said she was aware that the DP was facing an uphill battle.

“As we hit the campaign trail, we’ve been jeered at, or seen our fliers ripped up by passers-by right in front of us,” she said. “But we will do our best to get all of our candidates elected.”