Democrats and Republicans in four states are still looking for candidates as filing deadlines loom just days or weeks away.
Vermont’s other U.S. Senator is also on the ballot in 2016 – and is climbing the list of all-time service in the nation’s upper legislative chamber.
Just six sitting justices from the Badger State have been defeated at the ballot box over the last 164 years.
Wisconsin is the only state to back the eventual nominee from both parties in every cycle since 1972, save for a non-binding Democratic beauty contest primary in 1984.