The Maryland General Assembly passed legislation early Wednesday morning that would allow a Las Vegas-style casino in Prince George’s County, sending the controversial measure to Gov. Martin O’Malley (D) for his promised signature.

The bill would also allow table games, such as blackjack and roulette, at the state’s approved slots locations — transforming Maryland in a few short years into one of the most concentrated casino markets outside Las Vegas.

Voters would get the final say in November on whether the plan goes forward, following what is expected to be a multimillion-dollar advertising campaign.

The measure cleared the House 71 to 58 — the bare minimum required for passage — at about 11:45 p.m. Tuesday. About half an hour later, the Senate, which approved a similar bill last week, signed off on the House changes by a vote of 32 to 14. That brought to an end a special session called by O’Malley, who is expected to hold a bill-signing ceremony at 10 a.m. Wednesday.

Boosters of the plan, including Senate President Thomas V. Mike Miller Jr. (D-Calvert) and Prince George’s County Executive Rushern L. Baker III (D), have touted the promise of thousands of new jobs and tens of millions of dollars in additional revenue flowing to the state and host counties.

“In the end, we will have a healthy, competitive marketplace,” House Majority Leader Kumar P. Barve (D-Montgomery) told his colleagues toward the end of a floor debate that stretched over more than seven hours.

Opponents have warned that Maryland risks an oversaturated gambling market in which some of its emerging, large-scale casinos are destined to fail.

The plan attempts to compensate owners of other casinos for the new competition by letting them keep a larger share of slots proceeds than under current law.

That prompted some lawmakers to question why the legislature was giving casino owners a break after passing a series of tax hikes in recent years, including an income tax increase on six-figure earners this spring.

“I think that’s disgraceful,” said Del. Herbert H. McMillan (R-Anne Arundel). “If cutting taxes for casinos is great policy, then why aren’t we doing it for everyone else?”

By the time a Prince George’s venue is supposed to open, in mid-2016, motorists traveling along a 44-mile stretch of Route 295 would have three large casinos to choose among, each with more slot machines than any single casino on the Vegas Strip.

A gambling venue at National Harbor, the most likely site of a Prince George’s casino, would be among the first things people see upon crossing the Woodrow Wilson Bridge into Maryland. MGM Resorts has been lined up as the operator.

The state’s largest venue, Maryland Live!, which opened in June at an outlet mall in Anne Arundel County, raked in $35 million in revenue last month. Caesars Entertainment has been given the go-ahead to build another venue scheduled to open in downtown Baltimore in 2014. And three other smaller facilities are open or in the works elsewhere in the state.

The plan, which was proposed by O’Malley, would be the largest expansion of gambling in Maryland since voters authorized five slots locations in 2008.

Legislative analysts estimate that the expansion plan would net the state about $200 million a year in gambling revenue once a Prince George’s facility opens in mid-2016. Most of that — about $130 million — is unrelated to the Prince George’s facility, however.

That figure would drop by about $32 million under the House plan compared with the Senate bill.

In what appeared to be a bid to pick up additional votes for the underlying bill, the House agreed to an amendment Tuesday that could significantly expand the number of veterans organizations allowed to offer up to five lottery devices that are similar in appearance to slot machines. The provision, which has long been a priority for VFW halls and American Legion posts, was approved on a voice vote after some testy debate.

Some counties, including Montgomery, were not included in the amendment at the insistence of local lawmakers. Prince George’s is among those included.

O’Malley’s gambling plan will be on the ballot statewide in November, but Prince George’s is certain to be the epicenter of an expected multimillion-dollar ad campaign.

That’s because a provision in the bill only allows a casino to move forward in Prince George’s if a majority of county voters support the measure, regardless of the statewide tally.

Given that dynamic, the ideal outcome for some gaming companies operating in Maryland would be for the measure to carry statewide but fail in Prince George’s. That way, the operators would get table games but wouldn’t face additional competition from a site better situated to draw patrons from the District and Virginia.

The bill’s passage also underscored the clout O’Malley retains in Annapolis.

As his national political travels have increased in recent months, so too has grumbling among lawmakers that he is more interested in positioning himself for national office than tending to matters back home.

A few high-profile O’Malley initiatives fell short in the regular session — including a transportation plan that went nowhere — and the governor shared some of the blame for a final-night debacle that brought down both a major tax bill and gambling proposal.

Weeks later, O’Malley announced a pair of special sessions to mop up work on those two issues, pressing forward on gambling despite a lack of enthusiasm from House members.

O’Malley himself had dismissed an expanded gambling proposal during the regular session as a distraction, and as recently as last week, he proclaimed that he was “so sick” of the issue that he just wanted to put it behind him.

Nevertheless, O’Malley developed a new proposal and prodded delegates to accept a long-standing priority for the Senate president.

The bill would invite bids for a Prince George’s site from a swath of the county that includes both National Harbor and Rosecroft.

Baker has championed a site at National Harbor, the 300-acre mini-city on the Potomac River, drawing protest from Penn National Gaming, the owner of Rosecroft, a horse track in Fort Washington.

As envisioned, a casino at National Harbor would sit atop a wind-whipped hill just to the east of the heart of the development.

Penn has pledged it would build a new, state-of-the art facility at Rosecroft.

Even though it would be eligible for a Prince George’s license, Penn has called the process in Maryland “sleazy,” and signaled that the company is willing to pour millions into efforts to defeat the referendum.

Penn also has an out-of-state interest to protect. It is the owner of a full-fledged casino in Charles Town, W.Va., that stands to lose more of its Maryland customer base if a facility pops up in Prince George’s.

Aaron C. Davis contributed to this report.