I could see him still being a senator like Grassley, only retiring next year because of his cancer diagnosis.
This - I think he’d probably be a lifer.
I think the real question is whether Elizabeth Dole still ends up in the Senate. I could see her taking one of the Kansas seats if Bob retired in the 00s or 10s, but I doubt the couple would serve concurrently, and especially not from different states.
I feel like someone else, potentially Burr would've taken the seat Dole held. In that case I feel like Burr runs for his old seat and loses in 2008 similar to Dole IOTL and then in 2014 he successfully runs and wins his old seat before retiring in 2020 and being replaced by either Tillis or one of the 2022 senate candidates.
