Kelly Shue and Erzo Luttmer (both at Harvard) consider the role of "misvoting" in elections. Apparantly, not everyone is capable of going into the voting booth and casting a vote for the candidate they intend to support. The study uses data from the 2003 California recall election, in which there was "quasi-random variation in candidate name placement on ballots." The authors show that "minor candidate's vote shares almost double when their names are adjacent to the names of major candidates."
This is evidence that voters routinely make mistakes when submitting their ballots. What's more, the authors find evidence that these mistakes are larger is precincts with more poorly educated and poor voters. Therefore, "a major candidate that disproportionally attracts voters from such [undereducation or poor] preceincts faces an electoral disadvantage."
The article is forthcoming in the American Economic Journal: Policy. Read the article.