New Party Sakigake
He was born in present-day Nagano City. Originally a member of the Liberal Democratic Party, he co-founded New Party Sakigake in 1993 and served as a senior advisor to Prime Minister Morihiro Hosokawa from 1993 to 1994. He later returned to the LDP and served as Director-General of the Economic Planning Agency under Prime Minister Ryutaro Hashimoto. Tanaka again served as a policy advisor to Hosokawa during his bid for Governor of Tokyo in the 2014 gubernatorial election.