Senator Jon Tester of Montana is up in 2024, and the Republicans in Montana don’t currently have a candidate who could beat him. Matt Rosendale lost to him in 2018 only because Matt Rosendale was a spectacularly bad candidate. And there’s no one on the horizon who is much better. The talent pool in Montana is very weak.
The President’s son, Don Jr., would be a great candidate. He’s been coming to Montana for years. He’s well liked there. He’s displayed good campaign skills, and would beat Tester easily.
He’d be a latecomer, and that would hurt. But if he’s honest about his affection for Montana and its people, he could win them over. He’d have to work his butt off, from one end of the state to another. But he could beat Tester. Any decent Republican candidate could beat Tester.
Would Don Trump enjoy the life of a U. S. Senator? Why the hell not? All you need to do is show up, and mouth off. Sounds like fun to me.