Nagatsuma gained nationwide prominence after exposing scandals involving Japan's bureaucracy, including widespread mishandling of the national pension records and the misuse of public funds for kickbacks.

He continued to be active in the Diet after leaving his cabinet post and became the chairman of the Welfare and Labour Committee in the House of Representatives in 2012.

[3] After then-party leader Banri Kaieda was defeated in the 2014 election, Nagatsuma entered the race to succeed him, but lost to Katsuya Okada.

[5][6] Less than three weeks after the conclusion of the leadership race, Prime Minister Shinzo Abe called for a snap general election in October.

Earlier on the day of the PM's declaration, Tokyo governor Yuriko Koike formed Kibō no Tō, intended to be a conservative alternative to the LDP.

Some were overturned, as in the case of former DPJ leaders Kan and Kaieda, who contested under the CDP banner and regained their seats.