Katsuya Okada
In August 2017, Hosono left the Democratic Party, the successor of the DPJ, with the intention to form his own political party. His reason for wanting to leave the party was because of its policy on security and amending the Constitution. In September, he collaborated with Tokyo governor Yuriko Koike and Diet member Masaru Wakasa to form a conservative opposition party named the Party of Hope. After the then-DP leader Seiji Maehara allowed party members to run under the Hope banner in the imminent general election, conservative-leaning DP representatives moved to Hope en masse. However, a significant bloc of ex-DP representatives were barred from running under the Hope ticket by then-party leader Koike. Several of these representatives then formed the Constitutional Democratic Party (CDP) to house liberal-leaning former DP members. Some chose to run as independents, including Yoshihiko Noda and Katsuya Okada.