No Appointment Necessary (in AZ, MD, UT, WI)
Over the last 100 years there have been 189 appointments made to the U.S. Senate to fill vacancies created for a variety of reasons such as retirement, death, or resignations to become president or vice-president. Kentucky leads the way with the most such appointments since the introduction of direct elections in 1913 with eight, followed by New Jersey, North Carolina, and South Carolina with seven, and Idaho and Minnesota with six. The state average is 3.8 appointments during this span, with the most recent being Nevada Republican Dean Heller to fill John Ensign’s seat earlier this year. Four states, however, have not had to appoint a single U.S. Senator over these last 98 years: Arizona, Maryland, Utah, and Wisconsin. Hawaii, Maine, and Oklahoma have appointed just one each.
If I am not mistaken, WI has NEVER permitted an interim gubernatorial appointment to fill a US Senate vacancy since the commencement of the direct vote in 1914 (every other state either still has, or had at some point in the past, empowered its governor such role; e.g. most recently, in 2015 or ’16, ND would revoke such power, in anticipation of a ‘governor Mary Kathryn Heitkamp’ filling her unexpired term with a member of her own Democratic Non-Partisan-League party). Also, barring a change in its statute or constitution, OK will have no Senate appointee other than Democrat James Howard Edmondson, who in the 1960s arranged his own appointment to the chamber.