This undated photo released by the Massachusetts Governor's office shows William "Mo" Cowan, right, former chief of staff for Gov. Deval Patrick. Uncredited/ASSOCIATED PRESS hide caption toggle caption Uncredited/ASSOCIATED PRESS The Two-Way Massachusetts Gov. Picks Short Term Replacement For Sen. John Kerry January 30, 2013 Gov. Deval Patrick selects former chief of staff William 'Mo' Cowan to become interim Mass. senator until a special June election is held to fill the seat.