 You're putting somebody in a position where they're taking over a can't-win situation. You'd much rather have it be the incumbent president who's defeated and you never have to think about it again. Why give somebody a big loss, whether it's Harris or even in the other options people talk about, Whitmer or Newsom, when you could run them in two years and try to build them up for an eight-year-long presidential arc? That's the part of it that I think is also not thought about enough as to why,