Massive losses by Japan's opposition parties in the February general election have created ambiguity over who represents the non-governing parties.
The Centrist Reform Alliance led by Junya Ogawa holds the most seats among opposition groups in the House of Representatives with just under 50. Yet Yuichiro Tamaki's Democratic Party for the People holds a combined 53 seats across both chambers.
Under Japan's system the opposition with the most seats in each house handles Diet business talks with the ruling party. The alliance fills this role in the lower house while its ally the Constitutional Democratic Party of Japan does so in the upper house.
Tamaki told reporters that his party alone exceeds 50 seats combined and therefore bears responsibility to challenge the government. Ogawa said he respects the larger total while maintaining the weight of his lower house position.
In last week's leaders debate Tamaki received a 12-minute slot and Ogawa received 10 minutes. Media outlets differ in their rankings with Kyodo News prioritizing lower house numbers and NHK treating the Democratic Party for the People as larger.