Tasso joined the Ministry of Foreign Affairs in 1988, receiving a master's degree in international relations from Johns Hopkins University in the United States while with the ministry.

In 1996, he was elected to the House of Representatives in the Diet (national legislature) for the first time as a member of the New Frontier Party and subsequently served as a diet member for the Democratic Party of Japan.

He was first elected governor of Iwate prefecture in 2007 and as of 2012 is in his second four-year term.

[1] On July 9, 2012, he announced that he would sever his ties with the DPJ and join Putting People's Lives First, the new party led by Ichiro Ozawa.

[1][2] Aichi: Hideaki Ōmura Akita: Norihisa Satake Aomori: Sōichirō Miyashita Chiba: Toshihito Kumagai Ehime: Tokihiro Nakamura Fukui: Tatsuji Sugimoto Fukuoka: Seitaro Hattori Fukushima: Masao Uchibori Gifu: Hajime Furuta Gunma: Ichita Yamamoto Hiroshima: Hidehiko Yuzaki Hokkaidō: Naomichi Suzuki Hyōgo: Motohiko Saitō Ibaraki: Kazuhiko Ōigawa Ishikawa: Hiroshi Hase Iwate: Takuya Tasso Kagawa: Toyohito Ikeda Kagoshima: Kōichi Shiota Kanagawa: Yūji Kuroiwa Kōchi: Seiji Hamada Kumamoto: Takashi Kimura Kyoto: Takatoshi Nishiwaki Mie: Katsuyuki Ichimi Miyagi: Yoshihiro Murai Miyazaki: Shunji Kōno Nagano: Shuichi Abe Nagasaki: Kengo Oishi Nara: Makoto Yamashita Niigata: Hideyo Hanazumi Ōita: Kiichiro Satō Okayama: Ryuta Ibaragi Okinawa: Denny Tamaki Osaka: Hirofumi Yoshimura Saga: Yoshinori Yamaguchi Saitama: Motohiro Ōno Shiga: Taizō Mikazuki Shimane: Tatsuya Maruyama Shizuoka: Yasutomo Suzuki Tochigi: Tomikazu Fukuda Tokushima: Masazumi Gotoda Tokyo: Yuriko Koike Tottori: Shinji Hirai Toyama: Hachiro Nitta Wakayama: Shūhei Kishimoto Yamagata: Mieko Yoshimura Yamaguchi: Tsugumasa Muraoka Yamanashi: Kotaro Nagasaki