Preston Parks was a faithless elector during the 1948 United States presidential election.
A member of the Tennessee Democratic Party, Parks was chosen by his party as an elector for Democratic nominees - Harry S. Truman and Alben W. Barkley. However, he actively campaigned for the Dixiecrats, a splinter group of segregationist Southern Democrats, who ran their own (Strom Thurmond/Fielding L. Wright) ticket, opposing Truman's civil rights policy.
This made Parks the only elector pledged to one party who had campaigned for another ticket. Truman carried Tennessee but Preston, although formally pledged to him, cast his vote, as vowed, on Thurmond and Wright. The other Democratic Tennessee elector took the same vow as Parks, but ultimately voted for the Democratic Party ticket.
Parks' sole faithless vote, in addition to votes from States carried by Thurmond (South Carolina, Mississippi, Alabama and Louisiana), gave the Dixiecrat ticket a total count of 39 votes in the electoral college.