Does Malapportionment Favor the Republican Party?

Abstract

Abstract This paper examines electoral bias within US politics, including as it relates to malapportionment in the US Senate and Electoral College. Specifically, with the Republican Party gaining significant support in rural areas and the Democratic Party becoming concentrated in urban areas, there is concern that the US electoral system increases the probability that the Republican Party will win a much higher percent of Senate seats than its public support and repeatedly win the presidency without having won a plurality of votes, as was the case in 2000 and 2016. I explore this concern using a relatively new measure called the Directional Proportionality Index (DPIx). Applying it to the Electoral College since 1872 and the US Senate since 1918, this paper demonstrates that while there does exist a small pro-Republican bias in the Electoral College owing to malapportionment, the pro-Republican malapportionment bias in Senate races is far more substantial. However, as long as the percent vote for Democratic and Republican presidential candidates remains close due to partisan polarization, this small bias in the Electoral College is likely enough to lead to more cases whereby the Republican Party loses the popular vote but still wins control over the White House and the United States Congress.