International Center for Policy and Conflict (ICPC) now wants Migori Governor Okoth Obado to resign.
In a statement on Saturday, the lobby said the county chief has failed to respect the values and principles of the Constitution.
The ICPC said Mr Obado lacks in character and integrity as demonstrated by the various allegations currently surrounding him.
Governor Obado was arrested on Friday and will be charged on Monday with the murder of Rongo University student Sharon Otieno.
His lawyer Cliff Ombeta confirmed the charges saying the governor would spend the weekend in police custody.
The lawyer indicated the governor's wife Hellen was also a person of interest as suspects named her close associates in the horrendous scheme.
ICPC Executive Director Ndung'u Wainaina said: "Governor Obado must fully understand that the conduct of state officers in private and public is very central in determining whether they have the required integrity and suitability to hold office."
He added: “In any case, when your conduct leads you to reasonable suspicion from a law enforcement agency to prefer a charge to be drawn against you, your integrity is called to question. This is the situation of Governor Okoth Obado. He must resign."
He went on to say that Governor Obado cannot discharge Article 129 of the Constitution under the current circumstances, as they require that executive authority be exercised in a manner compatible with the principle of service to the people of Kenya and their well-being.
Mr Wainaina also cited the benefits and principles of leadership and integrity under sections 9 and 10 of the Public Officers Ethics Act.