Senator Sunday Olawale Fajinmi was elected a Senator in 1998 representing Osun west senatorial district on the platform of the United Nigeria Congress Party (UNCP) during General Sani Abacha's military regime.

After democracy was restored, in June 1999 he was again elected Senator, Osun west on the platform of the  Alliance for Democracy beating Isiaka Adetunji Adeleke of the People's Democratic Party.

While in the senate, he was appointed to the Science & Technology, Transport, State & Local Government (Vice Chairman), Information, Government Affairs and Economic Affairs committees.

In December 2005 he moved over to the ruling People's Democratic Party (PDP).

Fajinmi was the Alliance for Democracy gubernatorial candidate in the 9 August 2014 Osun State election.
Senator Sunday Olawale Fajinmi was elected a Senator in 1998 representing Osun west senatorial district on the platform of the United Nigeria Congress Party (UNCP) during General Sani Abacha's military regime. 
After democracy was restored, in June 1999 he was again elected Senator, Osun west on the platform of the  Alliance for Democracy beating Isiaka Adetunji Adeleke of the People's Democratic Party.
While in the senate, he was appointed to the Science & Technology, Transport, State & Local Government (Vice Chairman), Information, Government Affairs and Economic Affairs committees.
In December 2005 he moved over to the ruling People's Democratic Party (PDP).
Fajinmi was the Alliance for Democracy gubernatorial candidate in the 9 August 2014 Osun State election.
Sunday Fajinmi