Kyl's resignation is effective December 31; McSally likely to be sworn in when the new Senate convenes in January.
He becomes the first incumbent Senator to announce their retirement in the new election cycle
Gov. Doug Ducey will appoint a replacement, who will serve until a special election in 2020
GOP will be defending 22 seats vs. just 9 in 2018, although most of those are in deep red states.
Former Massachusetts Gov. Deval Patrick and attorney Michael Avenatti have been removed from the list