Legislation that would allow for slot-machine like devices that pay out based on historical horse racing outcomes is sparking a fight between traditional casinos in Massachusetts and a group looking to put the devices in the Boston area.

The Massachusetts House of Representatives authorized the new form of betting as part of an economic development bill passed in July, while the Senate left it out of its version of the legislation. Senior legislative leadership is now deciding whether to include it in the final bill.

Three of the state’s casino operators, Wynn Resorts Ltd., MGM Resorts International and Penn Entertainment Inc., released an economic report on Monday saying the gambling expansion would take as much as $216 million in annual revenue from their businesses, which pay a higher tax rate than the new machines would, and cost as many as 1,074 casino jobs. The Mashpee Wampanoag Tribe, which operates a casino in East Taunton, Massachusetts, has also urged legislators to reject the measure.

The devices look very much like traditional slot machines. The difference is that whether a gambler wins or loses is determined by previously run horse races, rather than by the random number generators used by slot machines. The tracks, jockeys and names of the horses are hidden, so the player can’t know in advance who’ll win.

Slot machine manufacturers, including International Game Technology and Light & Wonder, make the devices. Exacta Systems, a division of Churchill Downs Inc., creates the systems that run the wagering. The games are often pitched to customers and politicians as a way to reinvigorate the racing industry.

The Massachusetts legislation is being pushed by Richard Fields, the largest investor in Suffolk Downs, a shuttered track in East Boston. Fields was part of a group that sought more than a decade ago to open a casino at the site, but the state instead awarded the license to Wynn in nearby Everett. The machines will ultimately generate over $100 million annually in tax revenue for healthcare in the state, according to backers.

“They just don’t want competition,” Fields said about casino opposition to the proposal. “They’ve rested on their laurels, and the product out there is mediocre.”Wynn Chief Executive Officer Craig Billings wrote in an Oct. 15 Boston Globe opinion piece that the state’s move to legalize the devices undermines legislation passed in 2011 that allows for a limited number of casinos and one slot-machine parlor. That’s the deal that prompted Wynn to invest $2.6 billion in its Encore Boston Harbor resort, he added.

“These are effectively slot machines operating under a different regulatory label,” Billings wrote.

Seven states offer historical horse racing presently, including Kentucky, New Hampshire and Virginia. While the footprint is limited, the devices are a growing segment of the overall gambling market, according to James Kilsby, chief analyst with Vixio Regulatory Intelligence.

The devices are part of a broader family of products that look like slot machines, but operate under the rules of other contests, such as bingo or the state lottery, allowing them to be played even in jurisdictions that don’t permit full-fledged casinos, Kilsby said.

The proposal would enable racing licensees in Massachusetts to operate the devices. Fields doesn’t plan to open a facility at Suffolk Downs, which is being redeveloped, but elsewhere in Suffolk County, potentially even in or near downtown Boston. That venue could host roughly 800 of the machines, with a similar number of employees, he said.

Fields has an agreement to buy a shuttered greyhound racing track in Raynham, roughly 30 miles south of Boston, that would also be eligible for historic horse racing under the bill. That facility would be smaller, with just north of 400 employees. It would be close to the Mashpee Wampanoag casino. Fields said he’d aim to work with the tribe to make it “a positive for them financially.”After Kansas legalized historical horse racing in 2022, Boyd Gaming Corp., which owns the Kansas Star Casino in Wichita, sued to block the devices, claiming they violated the state’s agreements with traditional casinos.

The case was ultimately dismissed and some 1,000 historical horse racing devices began taking bets at Gilley’s Gambling Hall in Park City last year.

Gilley’s took in $48.5 million in wagers in the first two months of the current fiscal year, according to the Kansas Racing and Gaming Commission. Revenue at the state’s four casinos was unchanged. A spokesperson for Boyd declined to comment, citing a quiet period before an upcoming earnings release.

Lydia Edwards, a Massachusetts state senator whose district includes Boston and Suffolk Downs, wants historical horse racing to undergo a more thorough review, with more opportunities for the public to weigh in, before she’d consider approving it.

“I’m hearing from people it’s a slot machine, I’m hearing from the proponents it’s not,” Edwards said. “I want as an elected official to make an informed decision.”