"While it is possible for a voter to inadvertently select a candidate, it is not possible for the machine to automatically select a candidate," Miller wrote.

Miller added that his office, along with the FBI and Nevada state attorney general's office, had investigated similar complaints in 2010. That probe concluded that any claims that Nevada's electronic voting machines malfunctioned or were pre-programmed lacked merit.

Gary Bartlett, executive director of North Carolina's State Board of Elections said the "rumors and hysteria" surrounding vote switching has centered on some incidents in the state's Guildford County.

Since early voting began on Oct. 18, voters reported 24 problems with the touchscreen Direct Recording Electronic (DRE) voting systems used in the county. In each of those incidents, the voters were able to review and change their votes before casting a ballot, Bartlett said in a letter sent Friday to the RNC.

There were a "handful" of problems reported in the 23 other counties that are using DRE machines, he said. But in each case, the errors were caught and corrected by the voter, he added.