A Priori Voting Power When One Vote Counts in Two Ways, with Application to Two Variants of the U.S. Electoral College

Abstract

The President of the United States is elected, not by a direct national popular vote, but by a two-tier Electoral College system in which (in almost universal practice since the 1830s) separate state popular votes are aggregated by adding up state electoral votes awarded, on a winner-take-all basis, to the plurality winner in each state. Each state has electoral votes equal in number to its total representation in Congress and since 1964 the District of Columbia has three electoral votes. At the present time, there are 435 members of the House of Representatives and 100 Senators, so the total number of electoral votes is 538, with 270 required for election (with a 269–269 tie possible). The U.S. Electoral College is therefore a two-tier electoral system: individual voters cast votes in the lower-tier to choose between rival slates of ‘Presidential electors’ pledged to one or other Presidential candidate, and the winning elector slates then cast blocs of electoral votes for the candidate to whom they are pledged in the upper tier. The Electoral College therefore generates the kind of weighted voting system that invites analysis using one of the several measures of a priori voting power. With such a measure, we can determine whether and how much the power of voters may vary from state to state and how individual voting power may change under different variants of the Electoral College system.