Calls have been growing from opposition parties urging Prime Minister Fumio Kishida to quickly dissolve the Lower House for a general election following his ruling Liberal Democratic Party's (LDP) thumping in three by-elections late last month.
Despite the calls, it remains unclear whether opposition parties will be able to join hands in the next general election for the all-important lower chamber of parliament.
In one example of the gaps between some opposition forces, the Constitutional Democratic Party of Japan, the largest opposition force, is expected to face off with Nippon Ishin no Kai in more than 100 single-seat constituencies.