In a dramatic move sure to change the landscape of the nation's politics, the center-left Democratic Party decided Thursday to effectively disband its Lower House caucus and join Kibo no To (Party of Hope), a new conservative party led by Tokyo Gov. Yuriko Koike.

The effective sudden death of the nation's largest opposition force could turn the Oct. 22 Lower House election into a two-way race between conservative forces: Prime Minister Shinzo Abe's Liberal Democratic Party and Kibo no To.

Public support for the DP has been dwindling for months, and the party was widely predicted to suffer a crushing defeat in the upcoming vote.