Jon Kyle's 68. Sure it's young by Senate standards where they can't let go of power until wheeled out in a body bag but maybe he's had enough. He'll have to give up leadership anyway because he'll be termed out as White and he's not going to be Minority (Majority?) leader.
For the GOP congressmen John Shadegg and Jeff Flake may consider a run.. Dems have a former AG and state party chair to run for it.