Campaign finance reports show the Las Vegas Sands is almost singlehandedly funding a ballot effort to break up NV Energy's monopoly.
The casino company previously declined to say whether it was involved with the Energy Choice Initiative, which would change the constitution to give customers the right to choose their energy provider and sell power to others.
Disclosure forms filed Tuesday show Sands contributed $500,000 to the initiative petition effort, which needs more than 55,000 valid signatures to qualify for the November ballot.
MGM Resorts contributed the remaining $10,000 to the effort's PAC.
Sands applied to leave NV Energy and fought against a $24 million exit fee imposed by regulators, but recently abandoned its application.
MGM is proceeding with its exit proposal and plans to pay an $87 million fee.