 After being re-elected in 2002, Groff was appointed to the Colorado Senate in February 2003 to fill the vacancy left by the resignation of Sen. Penfield Tate III; he became only the 6th African-American state senator in Colorado history, occupying the Senate seat previous held by his father, Sen. Regis Groff.Sometimes called the "Conscience of the Senate", and regarded as a "pragmatic and deliberative" leader, Groff was named Senate president "pro tem" in 2005.Following the resignation of Senate President Joan Fitz-Gerald in November 2007, Groff was tapped to become Senate President, and had already begun handling some of Fitz-Gerald's responsibilities during her Congressional campaign.