He was a member of the Democratic Party of Japan and served as the Vice-Speaker of the Lower House of the Diet.

Beginning his time at university in 1960, Nakano joined the Democratic Socialist Party.

In 1994, Nakano joined the New Frontier Party and served as Chair of the Policy Inquiry Commission.

He represented the Osaka 8 electoral district until 2012, when he lost to Nippon Ishin no Kai candidate Tomohiko Kinoshita.

Note: As part of Diet custom, the Speaker and Vice-Speaker of the House must formally secede from their party.