Tarō Nakayama started his career as a Diet member in 1968, elected as a member of the House of Councillors and a member of the Liberal Democratic Party (LDP). Before becoming a politician, he was a pediatrician. He switched membership to the House of Representatives in 1986. He lost his seat in the 2009 election of the House of Representatives. His parents also served in the Diet as legislators; his mother, Masa Nakayama, was the first female cabinet member.

In the late 1990s, Nakayama pushed to establish committees for constitutional discussion in both houses, leading the Diet Members Caucus for Promoting Constitutional Research (憲法調査推進議員連盟). He was appointed as the chairperson for the HR Research Commission on the Constitution (憲法調査会) and the HR Special Research Committee on the Constitution (日本国憲法に関する調査特別委員会) when each was established in the House of Representatives (in 2000 and 2005, respectively).

Nakayama thinks that the Japanese constitution should be revised because it was written by the United States and does not reflect Japan’s own history, values, or traditions. Mentioning some controversial topics that Japan faced as of 2003, such as the constitutionality of the status of the Self Defense Forces and the possibility of a female emperor, he urged that the constitution should be updated to respond to changing circumstances rather than extending interpretations of the constitution, highlighting that most countries have revised their constitutions.