Massachusetts Gov. Deval Patrick has appointed his former chief of staff to serve as interim senator in place of out-going Sen. John Kerry.
William "MO" Cowan, a North Carolina native, said he is "honored and humbled" to fill the seat left vacant by Secretary of State designate.
Cowan is the second African-American to represent the state of Massachusetts in the Senate.
He will serve in the position until voters elect a new senator in a special election June 25.