Maybe an achievement for completing every elector's personal quest (and/or interim achievements for completing a certain number of them)? I've been finding that the quests are often the least efficient way to get votes--but they're sometimes sources of cool lore or necessary clues--so more incentive to do them is always good, and doing them all would be quite the accomplishment! (The count would have to be cumulative across runs, obviously; some electors don't even offer their quest every time.)