A former Republican candidate for state representative pleaded not guilty to 12 criminal counts relating to voter fraud at his arraignment Wednesday in Hampden Superior Court in Springfield.

Enrico John Villamaino III is accused of masterminding a scheme alongside his wife, Courtney Llewellyn, to secretly change the party affiliation of more than 280 people and cast absentee ballots on their ­behalf, hoping to tip in his ­favor in September’s Republican primary for the state representative seat in the Second Hampden District, prosecutors said.