Abdullahi Adamu, national leader of the All Progressives Congress (APC), has lost his Nasarawa western senatorial seat to Ahmed Wadada, the Social Democratic Party candidate (SDP).
Nigerians flocked to the polls on Saturday to pick a president and members of the national legislature.
Adamu was unable to provide the APC candidate Shehu Tukur to replace him in the upper chambers.
In the zonal collation center in Keffi, Nasiruddeen Baba, the Independent National Electoral Commission (INEC) returning officer for Nasarawa west senatorial district, declared Wadada the victor.
Wadada received 96,488 votes, while Adamu received 47,730.
Peoples Democratic Party (PDP) candidate Musa Galadima received 46,820 votes, while Labour Party candidate Bala Tongurma received 33,220 votes.