Complexity of shift bribery for iterative voting rules

Abstract In iterative voting systems, candidates are eliminated in consecutive rounds until either a fixed number of is reached or the set remaining does not change anymore. We focus on systems based positional scoring rules plurality, veto, and Borda study their resistance against shift bribery attacks introduced by Elkind et al. [1] Kaczmarczyk Faliszewski [2]. constructive (Elkind [1]), an attacker seeks to make designated candidate win election bribing voters this preferences; destructive (Kaczmarczyk [2]), briber’s goal prevent candidate’s victory. show that many resistant these types attack, i.e., corresponding decision problems NP-hard. These include iterated plurality as well due Hare, Coombs, Baldwin, Nanson; variants Hare also known single transferable vote, instant-runoff voting, alternative vote.