South Carolina 2010 Democratic United States Senate Primary Election


For Election Day voting, South Carolina uses an electronic ballot system with no auditable, voter-verified record of votes. However, South Carolina’s absentee votes are cast with voter-marked paper ballots that can be manually counted after the election to check the accuracy of the optical scanner’s tallies. Without the ability to conduct risk-based post-election manual audits of Election Day tallies, the only available way to investigate for electronic vote count error in South Carolina is an indirect method — compare the tallies for absentee and Election Day tallies to look for suspicious-looking tallies consistent with a pattern produced by outcome-altering vote miscount. Such a suspicious pattern exists in the 2010 South Carolina Democratic US Senate primary contest.

Comparing South Carolina’s Three 2010 Democratic Primary Elections

Of the three Democratic primary elections, the greatest difference between the winning margins in the two different types of voting (absentee paper ballots and Election Day electronic ballots) occurs in the US Senate contest between candidates Greene and Rawl. Table 1 below provides the winning margins for the three Democratic primary contests for absentee and Election Day ballots. The margin for Election Day tallies is almost twelve times greater than for absentee tallies in the US Senate contest, the largest difference of any of the three contests. In fact, if the county-level absentee ballot margins are the more accurate reflection of voter intent, then the winner of the US Senate primary election could be Rawl rather than Greene.

Table 1. Comparison of 2010 South Carolina Democratic Primaries

US Senate SC Gov SC Sup. of Ed.
Absentee Ballot Overall Winning Margin Share 1.64% 37.50% 4.23%
Election Day Overall Winning Margin Share 19.38% 35.81% 12.93%
Ratio of Margins (Election Day)/ (Absentee) 11.81 0.96 3.06
Overall Winning Margin 17.9% 36% 12.3%
The Overall Margin if Election Day County-level Margins were the Same as the County Absentee Margins -0.7% The Winner Changes! 36.5% 9%

Even though the overall margin of absentee ballot tallies is 1.6%, favoring candidate Greene, this overall margin does not indicate who would be the winner if the county-level absentee ballot margins held for all votes because the relative number of votes cast by each method (absentee versus electronic ballot) in each county and the total number of votes cast in each county vary widely. Hence, to determine the above result, simply multiply the reported absentee ballot margin in each county times the number of Election Day votes in each county to determine the margin (in number of votes) in each county for the case that the absentee ballot tally margins truly represented how voters cast their ballots. Then add this margin to the reported absentee ballot margin (in votes) to determine the margin that would have occurred if the absentee ballots reflect true voter preferences.

In other words, as shown in Table 2 below, if the inauditable county-level Election Day voting margins were in truth equal to the margins in the county absentee-ballot tallies, then Rawl rather than Greene would be the declared winner of the primary election for the Democratic candidate for the United States Senate.

Table 2: If the County-level Absentee Ballot Margins are the Correct Margins for Election Day Voting

Apparent Winner would Lose Apparent Runner-up would Win
US Senate Yes Yes
SC Governor No No
SC Sup. of Ed. No No


While it is physically impossible to verify who won any election in South Carolina due to its use of electronic-ballot voting, analysis of the available data shows that the reported Democratic US Senate primary election results are consistent with sufficient vote miscount to cause an incorrect election outcome. The outcome of the South Carolina Democratic primary election for the United States Senate candidate is in doubt.

A less costly voter-marked paper ballot system would improve South Carolina’s capacity to check the accuracy of its election outcomes.

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