Because someone in the media whispers to them “hey yeah but wouldn’t in be fun if instead you spent the next 6 weeks trying unseat your own nominee” and they go “TAHTS’ SUCH A GOOD IDEA” and get busy on it
No one intervenes if the system goes after a Democrat, so it can all just happen as normal
Got it. Yeah. I thought I had seen something like that. I just couldn’t find it on the spot just now when looking for it.