Although the Constitutional Progressive party still played an important role in some cases, along with the Liberal party (both parties acknowledged each other and were referred as people's parties at the time), such as taking actions to present petitions for the three major cases, and advocating a movement to unite for a common purpose, but both parties eventually couldn't get along with each other when they failed the movement to unite, and the Constitutional Progressive party supported a proposal to revise a treaty that Okuma presented as foreign minister of the first Ito government in 1888 (he became foreign minister under the Kuroda government as well).
三大事件建白運動・大同団結運動では旧自由党系と連携して民党の一翼を担うが、大同団結運動の失敗と1888年の大隈の第1次伊藤内閣の外務大臣(日本)入閣（黒田内閣でも留任）によって大隈の条約改正案を支持したことにより自由党との関係は再び微妙になる。