Candidates backed by the main opposition Constitutional Democratic Party of Japan are in the lead ahead of three by-elections for the House of Representatives on Sunday.

The ruling Liberal Democratic Party fielded its own candidate, Norimasa Nishikori, only in the by-election in the No. 1 constituency of Shimane Prefecture. For the remaining two elections — in Tokyo's No. 15 and Nagasaki Prefecture's No. 3 constituencies — the party gave up on running candidates of its own at a time when its intraparty factions are facing strong public criticisms over their long-exercised practice of creating slush funds.

In the one-on-one race in Shimane, where the LDP has dominated Lower House seats, the CDP's former lawmaker Akiko Kamei is gaining larger support than Nishikori, a rookie aiming to succeed a seat vacated by the death of former Lower House Speaker Hiroyuki Hosoda of the LDP. Kamei is getting support from the CDP and the Japanese Communist Party.