Japan’s Long-Dominant Party Suffers Election Defeat as Voters Swing Right

Japan’s long-governing Liberal Democratic Party suffered a defeat in parliamentary elections on Sunday that saw new right-wing populist groups make gains, heralding what could be a tectonic shift in what has been one of the world’s most stable democracies.

Prime Minister Shigeru Ishiba vowed to stay on after his Liberal Democrats and their coalition partner lost 19 of their 66 seats that were up for re-election, depriving them of control of the less powerful Upper House. But he is facing calls to step down after the setback left the Liberal Democrats, who have led Japan for all but five of the last 70 years, a minority party in both chambers of the Diet, the country’s Parliament.

Mr. Ishiba and his party failed to convince enough voters that they could resolve a host of challenges that included rising prices of staples like rice, tariff talks with the United States and the growing burden that supporting Japan’s aging population has placed on working-age people.

The election results exposed a growing generational fissure that is altering the nation’s politics. While two-thirds of the 124 seats up for grabs on Sunday went to opposition parties, the biggest gains were made not by the traditional liberal opposition, but by a gaggle of new parties that drew younger voters with stridently nationalist messages. Among them was Sanseito, a populist party led by a politician inspired by President Trump.

“With the L.D.P. in decline, Japan’s political landscape is diversifying,” said Romeo Marcantuoni, a Ph.D. candidate at Waseda University in Tokyo who has written about Sanseito. “For the first time, we’re seeing far-right populism similar to what we’ve seen in Europe.”

Before all the votes had even been counted, powerful members of the governing party were calling on Mr. Ishiba to step down, to take responsibility for what exit polls suggested would be a poor showing. Taro Aso, a former deputy prime minister, said he “couldn’t accept” Mr. Ishiba staying on as prime minister, TV Asahi reported.