Game concept
Voter Strength
The game also links it as Voting Strength, Voting Power, Vote Strength.
From the game's encyclopedia
Voter Strength represents the amount of influence that an Elector carries when voting in an elective Succession Law. This value usually increases depending on a ruler's Rank, but other factors may come into play depending on the Title's law.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Voter Strength is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Voter Strength represents the amount of influence that an Elector carries when voting in an elective Succession Law." The game also links it as Voting Strength, Voting Power and Vote Strength. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.