They can threaten any damn thing they like.
But if they move on from Nan they lose a Huge part of the base they've been cultivating forever through Balkanizing America into a myriad of Special Grievance Groups.
There's no seat in the House that's a more secure sinecure than Nan's, so she's perfect to placate the Antifa and BLM sympathizers.
Rep. Foghorn is the Poster Child for the "I'm Special so gimmee, gimmee, gimmee, Social Anarchy/SJW" voters they can't win without.