TOKYO (AP) -- The governing coalition of Prime Minister Shigeru Ishiba is likely to lose a majority in the smaller of Japan's two parliamentary houses in a key election Sunday, according to exit polls, worsening the country's political instability.

Voters were deciding half of the 248 seats in the upper house, the less powerful of the two chambers in Japan's Diet.

Ishiba has set the bar low, wanting a simple majority of 125 seats, which means his Liberal Democratic Party, or LDP, and its Buddhist-backed junior coalition partner Komeito need to win 50 to add to the 75 seats they already have.

That would mean a big retreat from the 141 seats they had before the election.

Exit poll results released seconds after the ballots closed Sunday night mostly showed a major setback for Ishiba's coalition. Japan's NHK television projected a range of 32-51 seats for the prime minister's coalition, while other networks projected it would win just over 40 seats.

The LDP alone is projected to win from 32 to 35 seats, the fewest won by the party, which still is the No. 1 party in the parliament.

"It's a tough situation. I take it humbly and sincerely," Ishiba told a live interview with NHK. He said that the poor showing was because his government's measures to combat price increase have yet to reach many people.

Ishiba showed his determination to stay on to tackle economic and security challenges.

"I will fulfill my responsibility as head of the No. 1 party and work for the country."

A poor performance in the election would not immediately trigger a change of government because the upper house lacks the power to file a no-confidence motion against a leader, but it would certainly deepen uncertainty over his fate and Japan's political stability. Ishiba would face calls from within the LDP party to step down or find another coalition partner.

Soaring prices, lagging incomes and burdensome social security payments are the top issues for frustrated, cash-strapped voters. Stricter measures targeting foreign residents and visitors have also emerged as a key issue, with a surging right-wing populist party leading the campaign.

Sunday's vote comes after Ishiba's coalition lost a majority in the October lower house election, stung by past corruption scandals, and his unpopular government has since been forced into making concessions to the opposition to get legislation through parliament. It has been unable to quickly deliver effective measures to mitigate rising prices, including Japan's traditional staple of rice, and dwindling wages.

U.S. President Donald Trump has added to the pressure, complaining about a lack of progress in trade negotiations and the lack of sales of U.S. autos and American-grown rice to Japan despite a shortfall in domestic stocks of the grain. A 25% tariff due to take effect Aug. 1 has been another blow for Ishiba.

Ishiba has resisted any compromise before the election, but the prospect for a breakthrough after the election is just as unclear because the minority government would have difficulty forming a consensus with the opposition.

Frustrated voters are rapidly turning to emerging populist parties. The eight main opposition groups, however, are too fractured to forge a common platform as a united front and gain voter support as a viable alternative.

The emerging populist party Sanseito stands out with the toughest anti-foreigner stance, with its "Japanese First" platform that proposes a new agency to handle policies related to foreigners. The party's populist platform also includes anti-vaccine, anti-globalism and favors traditional gender roles.

Conservative to centrist opposition groups, including the main opposition Constitutional Democratic Party of Japan, or CDPJ, the DPP, and Sanseito have gained significant ground at the Liberal Democrats' expense. The CDPJ was projected to win up to 26 seats, while the DPP could quadruple to 17 seats from four, exit poll results show. Sanseito is expected to surge to 16 from just one.

None of the opposition parties said that they were open to cooperating with the governing coalition. CDPJ leader Yoshihiko Noda told NHK that his priority is to form an alliance among the opposition.

The spread of xenophobic rhetoric in the election campaign and on social media has triggered protests by human rights activists and alarmed foreign residents.

LDP has almost continuously dominated Japan's postwar politics, contributing to its political stability and social conformity.

Voters are divided between stability and change, with some voicing concern about escalating xenophobia.

Yuko Tsuji, a 43-year-old consultant, who came to a polling station inside a downtown Tokyo gymnasium with her husband, said they both support LDP for stability and unity. and voted "for candidates who won't fuel division."

"If the ruling party doesn't govern properly, the conservative base will drift toward extremes. So I voted with the hope that the ruling party would tighten things up," she said.

Self-employed Daiichi Nasu, 57, who came to vote with his dog, said that he hopes for a change toward a more inclusive and diverse society, with more open immigration and gender policies such as allowing married couples to keep separate surnames.

"That's why I voted for the CDPJ," he said. "I want to see progress on those fronts."

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Reeno Hashimoto contributed to this report.