Although the Seiyu Party took charge of the government alternately with Rikken Minsei-to political party for the first several years of the Showa period, after Tsuyoshi INUKAI was assassinated in May 15th Incident in 1932, it was oppressed by the military and declined; the Seiyu Party suffered a devastating defeat in the 19th general election of members of the House of Representatives in 1936 including the president Kisaburo SUZUKI's failure.
昭和に入って数年は立憲民政党と交替で政権をになったが、1932年（昭和7年）、五・一五事件で犬養毅が暗殺されてからは軍部に圧迫されて衰退し、1936年の第19回衆議院議員総選挙では総裁の鈴木喜三郎が落選するなどの大惨敗を喫した。