TRENTON, N.J. — A record $20.8 million has been spent, so far, by interest groups for and against expanding casino gambling to northern New Jersey, state records released Monday confirm.

The Election Law Enforcement Commission on Monday said the spending was the highest on a referendum since the 1976 question on gambling in Atlantic City. Adjusted for inflation, about $5.6 million was spent on that question.

The Associated Press first reported the record spending last week, based on the interest groups’ documents that were received early.

The highest amount was spent by anti-expansion Trenton’s Bad Bet, which doled out $11.3 million. Its funders include Genting New York, which operates Resorts World Casino in New York and is a subsidiary of Malaysia-based Genting Malyasia Berhad.

Pro-expansion Our Turn NJ was financed by former Reebok chairman Paul Fireman and Meadowlands racetrack operator Jeff Gural. It spent about $8.5 million.

The group suspended its ad campaign last month citing internal polling that indicated the question would fail, but not before raising $10 million and spending all but $2.5 million.

Two New York unions spent a combined $1 million, opposed to the proposal.

Election commission executive director Jeff Brindle pointed out that four of the five most expensive ballot questions in state history revolved around casino gambling. The other question centered on raising the minimum wage.

“For those engaged in the casino arms race, it comes down to what is in their special interest. For the voters, it comes down to what is in the public interest,” Brindle said.

Brindle said spending on the proposal could top $40 million.