MGM Resorts International opens its $1.4 billion ­casino at National Harbor on Thursday night amid jackpot-level excitement and expectations for Maryland’s final and glitziest gambling palace.

Soaring 24 stories over the Potomac River and spanning five city blocks, the gleaming glass complex promises to deliver Las Vegas-style gambling, hundreds of millions in tax revenue and 4,000 new jobs.

But as thousands of people stream into MGM National Harbor for the first time, there is serious concern among industry analysts and fiscal watchdogs that Maryland and other states desperate for tax dollars have oversaturated the East Coast with casinos.

MGM National Harbor, just off the Capital Beltway near the Wilson Bridge, is Maryland’s sixth casino, with two others about an hour’s drive up Interstate 95 in Anne Arundel County and Baltimore. From Pennsylvania to Massachusetts, there are dozens more. At least seven additional casinos are to open by the end of 2018.

The problem, experts say, is that opening more casinos does not necessarily create more gamblers. Gallup surveys dating to 1996 show that the number of U.S. casino-goers has fluctuated between 24 percent and 30 percent of the population even as the number of states with casinos has swelled to 40.

The Washington Post was given an exclusive tour of the new MGM National Harbor before its grand opening on Dec. 8. (Ashleigh Joplin/The Washington Post)

Meanwhile, the industry is ­facing daunting demographic changes. Slot machine players — a large and highly profitable bloc — are aging, leaving casinos chasing younger customers who think slots are prehistoric and are content spending Friday nights playing iPhone poker while binge-watching “Westworld.”

“What you have is a bit of a perfect storm,” said Keith Foley, a gambling analyst for Moody’s Investors Service, who last year wrote a report titled “The Walls Are Closing In on Regional Casinos.”

In Maryland, casinos last year generated more than $487 million in tax revenue, a 16 percent increase from 2014, when the Horseshoe casino in Baltimore opened its doors. But that opening reverberated 13 miles away in Anne Arundel County, with Maryland Live’s state market share shrinking from 70 percent to 56 percent, according to data compiled by the Center for Gaming Research at the University of Nevada at Las Vegas.

Regionally, states are cannibalizing one another’s gambling business, siphoning tax revenue used for education and other public benefits. The most catastrophic example is Atlantic City, which is near bankruptcy because of casino expansion in Pennsylvania — which has suffered because of expansion of gambling in Maryland.

The Rockefeller Institute of Government, a policy research center at the State University of New York, issued a report this year warning about a “pattern of deterioration” in tax revenue because of the geographic expansion.

“States expand gambling in the hope that they’ll mimic the successes of early adopting states,” the report said, “but the more gambling expands, the more likely it is that economic and revenue gains will be eroded due to competition.”

Slot machines at the new MGM National Harbor casino. (Bill O'Leary/Washington Post)

Casino gambling on the East Coast became a case of “keeping up with the Joneses” in the early 2000s, as state legislators grew weary of watching potential tax dollars travel to Atlantic City casinos, then generating nearly $6 billion a year in revenue. Tight budgets during the Great Recession heightened interest.

Pennsylvania legalized casino-style gambling in 2006. Delaware, West Virginia, Maryland, New York and others quickly followed — either starting with slot machines or adding table games alongside existing slots. By 2013, there were 55 casinos, slot halls or racetrack locations with casino games in the Mid-Atlantic and Northeast.

“You have these dense locations all within close proximity with each other,” said Foley, the Moody’s analyst. “They all saw the potential of keeping this revenue within their own borders.”

If one casino was good, two were better, three were great — and now Maryland has six, making it one of the most concentrated casino markets in the country. State lawmakers have authorized 16,500 slot machines in the state, which is 12,407 square miles.

Maryland gaming officials acknowledge the abundance of gambling options.

“It’s very much a fact that the Northeast market is saturated, and that there is more supply coming on,” said Gordon Medenica, director of the Maryland Lottery and Gaming Control Agency.

But officials and casino executives say that Maryland’s geography is an advantage.

The state is at the very southern edge of the casino glut, with little competition beyond, particularly in Virginia, where casinos have been an impossible sell. That could change if legislators there get perturbed about losing tax dollars to Maryland casinos or if the newly recognized Pamunkey Indian tribe decides to open a gambling hall. MGM executives strenuously opposed federal recognition for the Pamunkey, a tiny tribe east of Richmond that claims Pocahontas as an ancestor.

MGM National Harbor is targeting the wealthy Northern Virginia suburbs. Company executives say that the ­Vegas-style resort offerings — celebrity chefs, a concert hall, more than 300 hotel rooms and luxury suites — will draw not just locals, but also tourists visiting the nation’s capital and even gamblers from other states with casinos.

“We think our integrated resort and casino is really unlike anything in this market,” said MGM National Harbor’s general manager, Bill Boasberg. “I think once we unveil the facility, people will really understand why we’ll be a such an attractive destination.”

The Horseshoe and Maryland Live will almost certainly be squeezed by the new casino, according to analysts. Lawmakers and gambling officials acknowledged as much in approving the MGM project, agreeing to sweeten revenue-sharing agreements for slot machines.

Horseshoe will keep 46 percent of slot revenue, up 7 percentage points. Maryland Live will keep 49 percent, up 8 percentage points. Medenica, the state’s gambling agency director, said taxpayers won’t lose because of the strong gains expected by MGM National Harbor — if, of course, it works out that way.

“Back in the day, it used to be that if you built a casino, people would come,” said Foley, the Moody’s analyst. “But nothing is a slam dunk anymore.”

Not only is there intense regional competition, but casino owners are also confronting demographic, technological and cultural changes in which the odds are not necessarily with the house. They built their businesses and organizational culture in a world of far fewer entertainment options.

David G. Schwartz, director of UNLV’s Center for Gaming Research, offered a personal example. He bought a copy of the hit video game Civilization V for $12.50. He has racked up more than 450 hours of playing time.

“That’s a ridiculously good buy,” he said. “You could spend $100 in a casino and not even last an hour.”

And it’s not just gambling.

It’s Netflix, which streamed 42.5 billion hours of content last year. It’s smartphones, which offer thousands of multiplayer games. It’s fantasy sports, now a multibillion-dollar industry. It’s online gambling, however that shakes out.

And it’s those hard-to-please millennials, who crave authentic experiences, transparency, and fairness — words not usually associated with casinos.

“When in a casino, the 35-and-younger demographic are much more likely to take part in non-gaming activities,” Alex Bumazhny, a Fitch Ratings analyst, wrote last year.

The problem is that restaurants, clubs and other amenities have much thinner profit margins than the casino floor. And if millennials want to eat foodie food or lounge at hip clubs, why would they drive (or take Uber) to a massive, crowded, noisy casino?

Ask these questions of just about anyone connected to casinos, and the answer almost always begins, “That’s a great question.”

One idea: skill-based games.

In Atlantic City, the Borgata added a basketball free-throw shooting contest. Other casinos are adding skill-based games to electronic slot machines — shooting, puzzles, less slot machine ding ding ding and more Angry Birds-style competition.

Maryland does not allow such games, but the state’s gambling agency says it is working on the issue.

Amid all the industry change and competition, Boasberg, the MGM National Harbor general manager, said one important aspect of life hasn’t and won’t change.

“We all still have a fundamental need to be entertained,” he said.

But where? And for how long?

In Maryland, after several months of year-over-year revenue growth at 3 percent or higher, revenue at the state’s casinos rose by just 0.8 percent in October. Maybe it’s just a momentary blip.

But given that the house always wins, one thing is certain: It’s not because the players are improving.