TRENTON, N.J. — Groups supporting and opposing casino expansion to northern New Jersey have spent a record sum of nearly $20 million to persuade voters ahead of the November ballot question, according to records obtained by The Associated Press.

State election officials say the spending could double between now and Election Day when voters will decide whether to approve expansion of casino gambling to two unspecified locations in the northern part of the state.

“It’s already set a record for ballot questions, and I’ve been saying we may see $40 million in spending,” Election Law Enforcement Commission executive director Jeff Brindle said.

Anti-expansion efforts outpaced spending by those who wanted to see casinos opened in the giant New York metro area.

Trenton’s Bad Bet, looking to defeat expansion, raised $11.6 million and spent $11.3 million from July through September. Its funders came mainly from groups with New York-based addresses, including Genting New York, which operates Resorts World Casino in New York and gave about $6 million. The group is a subsidiary of Malaysia-based Genting Malyasia Berhad.

“Trenton’s Bad Bet has received support from a diverse group of donors from within and outside the state of New Jersey who understand that casino expansion would result in the loss of tens of thousands of jobs and billions in economic losses for the entire region,” said Trenton’s Bad Bet spokesman Bill Cortese.

Our Turn NJ, which supported expansion but last month announced it would quit the effort, raised $10 million and spent $8.5 million. Its funding came from former Reebok chairman Paul Fireman and Meadowlands racetrack operator Jeff Gural.

Fireman and Gural said last month that based on internal polling, voters would reject the effort and they abandoned their multi-million dollar ad campaign.

Our Turn NJ spokesman Chris Donnelly credited Fireman and Gural for being transparent about their effort. “The opposition’s lack of transparency is just more proof that these Malaysian and New York gaming interests only care about protecting their own profits,” Donnelly said.

The spending far outpaces the previous record-holder, the 1976 effort to approve gambling in Atlantic City, according to Election Law Enforcement Commission documents. That effort topped $5.5 million, adjusted for inflation.

If approved, the new casinos would have to be at least 72 miles from Atlantic City and cost at least $1 billion apiece.

Tax revenue from the casinos would be shared among programs to help senior citizens, local communities, the horse racing industry and Atlantic City, which saw the Trump Taj Mahal close this week.

But no details of where the money would go, or how much there might be, have been presented to voters.

If the expansion is approved, Gural would partner with Hard Rock International to add a casino to the existing track in East Rutherford. Fireman has proposed building a massive casino resort in Jersey City, across the Hudson River from Manhattan, worth up to $5 billion.

The Associated Press obtained the records filed with the Election Law Enforcement Commission before they are set to become public next week. News of the documents was first reported by Politico.