Considering VA's significant military and government population...
"Reagan George, president of Virginia Voters Alliance, explained how this happens: “Say you move to Kansas and tell the election office there that you were registered in Virginia when you submit your Kansas voter-registration form. If the Kansas election official is bureaucratically lazy or politically motivated, your name never gets removed. The same thing can happen on the Virginia end, and you stay double-registered.”
How many of the 308,000 voters cast multiple ballots in a single election is not known."
"Don Palmer, secretary of the Virginia State Board of Elections, said efforts are being made to contact Virginia voters who have registered in other states.
Palmer said Virginia participates in two voter crosscheck programs and compares data with those of 30 other states, including Maryland, Delaware, North Carolina, Tennessee, Kentucky and West Virginia.
“Attempts to contact the identified voters who have registered in other states after their last activity date in Virginia—including registering to vote and voting—at both their current Virginia registration address and their out-of-state registration address are currently under way in accordance with the National Voter Registration Act and Virginia law,” Palmer said."
"working with Election Integrity Maryland—says it found 164 individuals who voted in both states in 2012.