Firing every elector in my cabinet on top of this finally caused an election deadlock! 11 votes for me, 13 for Lukomir, in the first round. Post-recess, 11 votes for me, 15 for Lukomir. No opportunity to cut and run though, just a game over assassination, but without any notified checks. Not sure if there's anything more I can do, or if that's just what happens after an election stalemate.
Strongly implied there is a situation I get to make a choice with "If you lose though, your options are fewer. He did give you a contact method and a promise of help. [...] thought exile was worth it. Will you? Of course, if you succeed, you won't need to make that choice.". Maybe that means I need to find a way to let Lukomir fully win, while still being primed to leave. Maybe I need fewer fully hostile enemies after a stalemate. Maybe it's not possible, and I jumped to conclusions.