Tsutomu Hata
Okada ran for the House of Representatives at the 1990 general election from LDP, representing Mie Prefecture's third district, and later joined the Takeshita faction of the Liberal Democratic Party, and followed faction leaders Tsutomu Hata and Ichirō Ozawa to join the Japan Renewal Party in 1993. Through a series of splits and mergers, Okada then became a member of the New Frontier Party, Sun Party, and Minseito, finally entering the DPJ upon its merger with Minseito in 1998.