保守新党
He was later a member of the Liberal Party, Conservative Party, and New Conservative Party, independent parties in coalition with the LDP. As Secretary-General of the NCP and part of the governing coalition, he served as Minister of Transportation under Keizō Obuchi and Yoshirō Mori. After the NCP merged with the LDP in 2003, Nikai became an LDP member again, and was appointed Director of the General Affairs Bureau in 2004.