Yukio Edano, 56, head of the CDPJ. (Photo: Reuters)

The party was formed on September 1 by merging the Constitutional Democratic Party of Japan (CDPJ) and the Democratic Party for the People (DPFP).

Candidates include Yukio Edano, 56, head of the CDPJ, and 46-year-old DPFP policy chief Kenta Izumi. The name and leader of the new party will be decided on Thursday.