What Voting Power Cannot Be

ABSTRACT “Almost everyone,” Ronald Dworkin wrote in Sovereign Virtue , “assumes that democracy means equal voting power.” What, then, is voting power? The standard view defines it as the probability that a vote changes the outcome assuming that each possible combination of votes is equiprobable. This has significant implications: institutions like the US Electoral College give disproportionate voting power to voters in large states. But the standard view cannot be true. As an a priori account, it rests on the principle of indifference, and thus faces the problem of multiple partitions: we could assign an equal probability to each possible combination of votes or to each possible vote share. The choice to partition in terms of combinations of votes is arbitrary, and makes the standard view objectionably overconfident. These problems of arbitrariness and overconfidence undermine the standard view's main implications. And they call into question whether equal voting power should play a central role in democratic theory.