i have a suspiciion that Ducey wants to be the Senator in 2022. That is why Kyl was perfect for him; someone who will easily win in 2020 but doesn’t want to be a long timer. If Kyl decides to leave in 2019, Ducey will want someone like that, a short timer. Not sure who that might be in AZ politics, but Ducey will cross that bridge when he comes to it. His preference would be to talk Kyl into staying til 2022.
It’s sort of like the Torricelli Switch, but with more options.