Japanese Prime Minister Shigeru Ishiba's ruling coalition is likely to lose its majority in the upper house, local media and exit polls projected on Sunday, in a result that could spell the end of his premiership and usher in heightened political uncertainty.

Ishiba’s Liberal Democratic Party (LDP) and its junior partner Komeito won around 41 of the 125 seats contested, falling short of the 50 needed to retain control of the 248-seat chamber, according to Nippon TV and TBS. 

NHK exit polls projected the coalition would win between 32 and 51 seats, while the right-wing populist Sanseito party made strong gains, securing 10 to 22 seats in addition to the two it already held.

The defeat compounds a series of setbacks for Ishiba, who came to power less than a year ago. Last October, his coalition was forced into a minority after losing control of the more powerful lower house in snap elections he called shortly after taking office.

If the exit polls are correct, the result would mark the first time since World War II that Japan’s ruling bloc is in the minority in both houses of parliament, significantly undermining its ability to pass legislation.

The loss also comes amid growing public discontent over inflation, shrinking pensions and stalled wages, as well as rising concerns about U.S. tariffs. A 25 percent tariff on Japanese exports, including autos, is set to take effect on August 1 if no deal is reached with Washington.

Despite repeated efforts, including high-level meetings with U.S. officials, Ishiba has failed to secure an agreement. His insistence on eliminating all tariffs has drawn criticism and is seen as a key obstacle to progress.

The LDP, which has governed Japan almost continuously since 1955, now faces deepening political and economic challenges as it grapples with a weakened mandate, a fragmented opposition and a surging populist right.

(With input from agencies)