AUGUSTA — The state Senate voted 20-10 Thursday to override Gov. Janet Mills’ veto of a bill to legalize sports betting.

The measure, passed by the Legislature in 2019, would open the door to both in-person and online sports betting in Maine, but the House will also have to vote to override, which requires a two-thirds majority, for the bill to become law, which could take place next week.

The bill was one of three that Mills, a Democrat, vetoed in January and was among 40 she had held since the last legislative session ended in June.

Thursday’s vote was largely bipartisan, with five Republicans joining 15 Democrats in voting to override. Seven Republicans and three Democrats voted to sustain.

The measure would give just about every entity with an interest in gambling a slice of the revenue. It faced no formal opposition in the Legislature beyond some concerns about problem gamblers. The bill would allow casino operators, off-track betting parlors, harness racing tracks and Native American tribes in Maine to host sports-betting operations. The measure would also allow online operators to apply for licenses allowing them to operate independently of casinos.

Mills’ veto message last month downplayed revenue considerations and focused on the harm the legislation could have on youth and low-income Mainers.

Casino operators in Bangor and Oxford lobbied lawmakers heavily in recent weeks to sustain the veto – they support a law that would require sports betting to be tethered to casinos. But a key sponsor of the bill, Sen. Louis Luchini, D-Ellsworth, urged his colleagues to override.

Luchini said limiting sports betting to casino-connected operations would be unfair because the casinos already enjoy a monopoly on gambling. He noted that since U.S. Supreme Court ruling ruled in 2018 that states have the right to regulate sports betting, 20 states have approved legalization.

Maine’s measure, L.D. 553, is a hybrid of seven bills that came to the Legislature in 2019, Luchini said.

New Hampshire recently legalized sports betting and in its first month of operations had taken in over $17 million in wagers, Luchini said.

Estimates of how much sports betting might be worth in Maine vary, but a fiscal note attached to the bill suggests that if it were fully implemented, the state would collect as much as $5 million a year in fees and taxes. However, sports betting revenue has fallen dramatically short of forecasts in several states that legalized it in 2018 and 2019.

“The rationale for these bills is largely because the illegal market in the U.S. is massive, as most of us know,” Luchini said. He said that, according to the American Gaming Association, the sports betting market in the U.S. is estimated at $150 billion a year, with 97 percent of that being conducted illegally.

“And anytime you bet through a bookie or an illegal online website, you run the risk that you don’t get paid because they just don’t have anybody to account to,” he said.

Opponents of the measure, including Sen. Scott Cyrway, R-Albion, said allowing online entities into the market in Maine is unfair to casino operators who have invested in the state, employed workers here and paid taxes in Maine.

“Where there is brick and mortar there is investment,” Cyrway said. He said Maine’s two casinos have invested more than $1 billion in the state and collectively employ over 1,000 workers.

Other opponents said they fear sports betting would only exacerbate problem gambling.

“Like substance abuse, gambling addiction is a real problem for Maine families,” said Sen. Stacey Guerin, R-Glenburn.

Luchini said Maine’s law takes that into account by taxing mobile sports-betting operators at 16 percent compared to 10 percent for those operating from physical locations in Maine. The bill also would require them to obtain the same licenses as casinos, direct funds toward problem gambling prevention, require the display of help-line information and allow the state’s Gambling Control Board to have strong oversight of sports betting marketing.

If the House votes to override, it will be the first time a Mills veto is overruled by the Legislature, where her party holds a majority in both bodies. Even so, it would be months before any legal sports betting could take place in Maine because the law would not go into effect until 90 days after the current Legislature adjourns in April or May.

Rule-making on the new law could also take several months to complete.