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.
"Improperly calibrated machines do not default in a manner that causes Republican votes to be recorded as votes for other candidates, Democratic or Libertarian," he wrote.
The software is programmed to highlight only those candidates whose names the voter actually touched. The machine may not accurately reflect the voter's intent if it has lost its calibration, Bartlett said. But as a safeguard every DRE voting system used in the state prompts the voter to verify their vote, he said.
Election watchdogs have for some time expressed concerns about DRE systems. Many academics, researches and election watchdog groups such as Verified Voting and Common Cause have said that such systems are prone to errors of the sort claimed by the RNC.
They have claimed that such machines are susceptible to tampering and accidental failure.
Many of the concerns are directed at DRE systems that lack so-called voter verifiable paper audit trails (VVPAT).
Election watchers have said that paperless DRE system pose a special threat to the integrity of the elections because they offer no easy way for a post election audit of the results. More than half of all states are scheduled to use DRE's to varying extents next Tuesday. Seventeen of them use paperless DREs in at least some areas.
Concerns about DRE systems aren't restricted to one party. During the 2008 presidential election, at least 16 voters in six counties in West Virginia reported having their votes for Obama being switched to votes for Sen. John McCain, according to a report by Verified Voting earlier this year. In June 2011, during the Democratic primaries in New Jerseys Cumberland County, a paperless DRE system attributed votes to the wrong candidates and ended up declaring the actual losers as winners of the election, according to Verified Voting.