Large-scale voting usability problems have changed the outcomes of several recent elections. The 2006 election in Sarasota County, Florida was one such incident, where the number of votes lost was nearly 50 times greater than the margin of victory for the US Representative race. Multiple hypotheses were proposed to explain this incident, with prevailing theories focused on malicious software, touchscreen miscalibration or poor ballot design, Study I aimed to empirically determine whether Sarasota voters unintentionally skipped the critical US Representative race due to poor ballot design. The Sarasota ballot was replicated initially, then header highlighting and number of races presented on the first screen were manipulated. While the presentation of multiple races had a significant effect on undervotes in the US Representative race, header highlighting did not. Nearly 20% of all voters (27 of 137) skipped the race their first time on that screen, an even greater undervote rate than that originally seen in Sarasota. In conjunction with other research, Study I results strongly suggests that the 2006 Sarasota election was almost certainly a human factors problem. A cognitive model of human voters was developed based on Study I data. Model predictions were then compared with behavioral data from Study 2, in which participants voted on a replica of the Charlotte County, Florida 2006 ballot.