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Right-Wing Populist Sanseito Strips Ruling Coalition of Upper House Majority

The July 20 vote handed Sohei Kamiya’s insurgent Sanseito party pivotal votes in a now-minority upper house coalition.

Sanseito party supporters raise their fists during the Sanseito's election campaign tour, on the last day of campaigning for the July 20 upper house election, at Shiba Park in Tokyo, Japan July 19, 2025.  REUTERS/Issei Kato/File Photo
Japan's Sanseito party leader Sohei Kamiya delivers a speech during the party’s rally in Tokyo, Japan, July 21, 2025, a day after the upper house election. REUTERS/Kim Kyung-Hoon/File Photo
Japan's opposition party Sanseito leader Sohei Kamiya smiles as he speaks to members of the media at the vote counting center in Tokyo on July 20, 2025. (Jiji Press/AFP via Getty Images)

Overview

  • Sanseito surged from one to 15 seats in the July 20 upper house election, ending the LDP-Komeito coalition’s six-decade dominance.
  • Without a majority in the 248-member chamber, Prime Minister Shigeru Ishiba’s government must negotiate backing on an issue-by-issue basis.
  • Ishiba has resisted calls to resign but now faces pressure from within the LDP over the coalition’s weakened mandate.
  • Sanseito leveraged YouTube, TikTok and other social media platforms to mobilize younger voters frustrated by economic stagnation and demographic decline.
  • Under Sohei Kamiya’s “Japanese First” banner, the party is pushing strict immigration curbs, constitutional revision and expanded imperial authority.