(Sarah L. Voisin/The Washington Post)

MGM National Harbor has helped boost the state’s overall gaming revenue since it opened Dec. 8, but the newcomer appears to be eating into the profits of Maryland’s other top casinos.

Monthly casino revenue rose an average of 37.8 percent in Maryland since MGM began operating, according to the state Lottery and Gaming Control Agency’s year-to-year comparisons. The industry, which sends some of its profits to fund schools and other public programs, set its record in the state by generating $141 million in March.

But monthly revenue for Maryland’s five other casinos has dropped an average of 11.8 percent since December, largely driven by dips of 9.4 percent for Horseshoe Casino in Baltimore and 16.6 percent for Maryland Live in Anne Arundel County — the two gaming facilities closest to MGM.

Casino officials and elected leaders say they are not alarmed by the numbers, which fall roughly in line with the projections made by state consultants after Maryland voters legalized table games and approved the addition of a sixth casino in a 2012 referendum.

“These people are still raking in money, just less than they would have otherwise,” said Del. Eric G. Luedtke (D-Montgomery), who co-chairs the state legislature’s gaming-oversight committee.

Maryland Live generated $46 million from slots and table games in May, while Horseshoe pulled in $24 million. Those totals, while hefty, represent declines of 22.3 percent and 18.1 percent, respectively, compared with the same period last year.

MGM, which has consistently outperformed all other casinos in the state since its first full month of operations, pulled in about $51 million.

A poker game at the opening of MGM National Harbor in December included Chad Power, left, who is a pro gambler and was based at Maryland Live casino before MGM opened. (Sarah L. Voisin/The Washington Post)

“Obviously, the presence of a new casino in Maryland has an effect on the revenues of the existing casinos,” said Jonathan Cordish, principal and finance director for the Cordish Cos., which owns and operates Maryland Live. “We will continue to compete and reinvest for the long term.”

A $200 million expansion of Maryland Live scheduled for completion next year includes a new 17-story hotel and convention center with a high-end spa, spaces for live entertainment and private gaming, and new restaurants. The casino also has been offering special promotions, including giving away five Tesla electric cars for its anniversary this month and guaranteeing jackpots up to $100,000 every weekend in June.

Horseshoe is banking in part on its participation in the country’s oldest nationwide player loyalty and rewards program, run by parent company Caesar Entertainment, to remain competitive in a crowded market. Officials with the casino say the establishment’s proximity to Baltimore sports stadiums, and the city’s plans for a new entertainment hub in the surrounding area, could help as well.

“As the southern gateway expands and becomes a diverse entertainment district, Horseshoe is poised to take advantage of the significant growth and development,” said Erin Chamberlin, the casino’s senior vice president and general manager.

When they approved the gambling expansion in 2012, state lawmakers gave Maryland Live and Horseshoe lower tax rates than MGM for slots revenue, acknowledging that the two older establishments were likely to be most affected by the launch of the new venue in Prince George’s County. MGM pays a rate of 56 percent, compared to 51 percent for Maryland Live and 54 percent for Horseshoe.

Industry experts say West Virginia casinos also have reason to be concerned about Maryland’s 2012 gambling expansion, because they now have to compete with venues across the border that offer table games rather than just slots.

Horseshoe, Maryland Live, MGM National Harbor and Rocky Gap Casino, located in Allegany County, are all less than 80 miles from Hollywood Casino at Charles Town Races.

Rocky Gap Casino, located in Allegany County, has continued to thrive since MGM opened, with monthly gaming revenue up an average of nearly 10 percent since December compared with the same period a year before. The Casino at Ocean Downs, which does not have table games and is located on the Eastern Shore, has seen an average monthly increase of more than 3 percent over that span.

The Hollywood Casino Perryville, in Cecil County, saw a decline, with its monthly revenue from slots and tables dropping an average of 3.5 percent.

Casino gambling generated more than $1 billion in gross revenue for the state in fiscal 2016, with 35 percent of that going to the state’s Education Trust Fund, 5 percent to horse racing, nearly 4 percent to grants for local jurisdictions affected by casinos and about 1 percent for Maryland’s small, minority- and women-owned businesses account.

This year, industry lobbyists successfully pushed state lawmakers to approve legislation that allows gaming establishments to carry over losses on slots and table games from one day to the next for purposes of determining how much they owe to the state.

Legislative analysts estimated that the measure could reduce revenue for the Education Trust Fund by more than $1.8 million a year. But supporters said it would encourage casinos to offer more high-stakes games by reducing their potential losses, in turn attracting more big-money players and increasing revenue in the long run.

Luedtke suggested that there will be little appetite for similar breaks in 2018.

“I doubt the legislature is in any mood to cut taxes for casinos, and I think the casinos know that,” he said.

Cordish said Maryland Live will not seek legislative or regulatory changes next year.