TOKYO (AP) – Japanese Prime Minister Sanae Takaichi’s governing party secured a two-thirds supermajority in parliamentary elections, Japanese media reported, citing preliminary results. The landslide victory was due, in large part, to the extraordinary popularity of Japan’s first female prime minister, and allows her to pursue a significant conservative shift in Japan’s security, immigration and other policies.

Ms. Takaichi, in a televised interview with public television network NHK following her victory, said she will emphasize policies meant to make Japan strong and prosperous.

NHK, citing vote count results, said Ms. Takaichi’s Liberal Democratic Party, or LDP, alone secured 316 seats by early Monday, comfortably surpassing a 261-seat absolute majority in the 465-member lower house, the more powerful of Japan’s two-chamber parliament. That marks a record since the party’s foundation in 1955 and surpasses the previous record of 300 seats won in 1986 by late Prime Minister Yasuhiro Nakasone.

With 36 seats won by its new ally, Japan Innovation Party, Ms. Takaichi’s ruling coalition has won 352 seats.

A smiling Ms. Takaichi placed a big red ribbon above each winner’s name on a signboard at the LDP’s headquarters, as accompanying party executives applauded.

Despite the lack of a majority in the upper house, the huge jump from the preelection share in the superior lower house would allow Ms. Takaichi to make progress on a right-wing agenda that aims to boost Japan’s economy and military capabilities as tensions grow with China and she tries to nurture ties with the United States.

Ms. Takaichi said she would try to gain support from the opposition while firmly pushing forward with her policy goals.

“I will be flexible,” she said.

Ms. Takaichi is popular, but the LDP, which has ruled Japan for most of the last seven decades, has struggled with funding and religious scandals in recent years. She called Sunday’s early election after only three months in office, hoping to turn that around while her popularity is high.

Popular Leader

The ultraconservative Ms. Takaichi, who took office as Japan’s first female leader in October, pledged to “work, work, work,” and her style, which is seen as both playful and tough, has resonated with younger fans who say they were not previously interested in politics.

The opposition, despite the formation of a new centrist alliance and a rising far-right, was too splintered to be a real challenger. The new opposition alliance of LDP’s former coalition partner, Buddhist-backed dovish Komeito, and the liberal-leaning Constitutional Democratic Party of Japan, is projected to sink to half of their combined preelection share of 167 seats.

Ms. Takaichi was betting with this election that her LDP party, together with its new partner, the JIP, would secure a majority.

U.S. President Donald Trump in a post on his Truth Social platform Sunday congratulated Ms. Takaichi “on a LANDSLIDE Victory in today’s very important Vote. She is a highly respected and very popular Leader. Sanae’s bold and wise decision to call for an Election paid off big time.”

Akihito Iwatake, a 53-year-old office worker, said he welcomed the big win by the LDP because he felt the party went too liberal in the past few years. “With Takaichi shifting things more toward the conservative side, I think that brought this positive result,” he said.

Takaichi’s Policies

The LDP’s right-wing partner, JIP leader Hirofumi Yoshimura, has said his party will serve as an “accelerator” for Ms. Takaichi’s push to conservative policies.

Japan has recently seen far-right populists gain ground, such as the anti-globalist and surging nationalist party Sanseito. Exit polls projected a big gain for Sanseito.

The first major task for Ms. Takaichi when the lower house reconvenes in mid-February is to work on a budget bill, delayed by the election, to fund economic measures that address rising costs and sluggish wages.

Ms. Takaichi has pledged to revise security and defense policies by December to bolster Japan’s offensive military capabilities, lifting a ban on weapons exports and moving further away from the country’s postwar pacifist principles.

She has been pushing for tougher policies on foreigners, anti-espionage and other measures that resonate with a far-right audience, but ones that experts say could undermine civil rights.

Ms. Takaichi also wants to increase defense spending in response to Mr. Trump’s pressure for Japan to loosen its purse strings.

She now has time to work on these policies, without an election until 2028.

Though Ms. Takaichi said that she is seeking to win support for policies seen as divisive in Japan, she largely avoided discussing ways to fund soaring military spending, how to fix diplomatic tension with China and other issues.

Despite her rightward shift, Ms. Takaichi is expected to maintain good relations with South Korea, given shared worries about threats from North Korea and China. But Seoul would worry about a Japanese attempt to revise the country’s pacifist constitution or to further build up its military because of Japan’s wartime past, said Leif-Eric Easley, professor of international studies at Ewha Womans University in Seoul.

In her campaign speeches, Ms. Takaichi enthusiastically talked about the need for government spending to fund “crisis management investment and growth,” such as measures to strengthen economic security, technology and other industries. Ms. Takaichi also seeks to push tougher measures on immigration, including stricter requirements for foreign property owners and a cap on foreign residents.