Many players have a lot at stake in Maryland’s debate over expanded gambling, but Gov. Martin O’Malley may have taken the biggest roll of the dice on Friday.

O’Malley (D) announced a special legislative session, to start Aug. 9, on whether to allow a Las Vegas-style casino in Prince George’s County, as well as table games, such as blackjack and roulette, at Maryland’s other slots locations.

But he did so with no guarantee that there are enough votes in the House of Delegates — which has balked at similar plans in recent months — and without sharing some key details of the legislation, which remains a work in progress. All of which means there’s a chance he could be disrupting legislators’ summer plans for nothing.

“I think it’s a pretty big gamble for him,” House Majority Whip Talmadge Branch (D-Baltimore), said of O’Malley. “Right now, I would say the votes are not there in the House. . . . A lot will depend on what the bill looks like, whether it’s fair to other operators.”

At a news conference in Annapolis, O’Malley cast the expansion as a way to create more construction and hospitality jobs while ending a bitter legislative debate.

“It’s time we act, and it’s time we put this issue behind us,” he said.

House Speaker Michael E. Busch (D-Anne Arundel), who acknowledged that he is “not a huge proponent” of gaming, told reporters he is “absolutely” confident that a bill can pass in his chamber with a few weeks’ work, a sentiment echoed by O’Malley aides.

There is concern among some legislators that a Prince George’s casino would harm Maryland Live!, the state’s largest casino, which opened last month in Anne Arundel County. Its owner, the Baltimore-based Cordish Cos., has vigorously fought the prospect of a Prince George’s casino — most likely at National Harbor — arguing that it would unfairly cut into its market in the Washington region.

How much tax relief Cordish and other operators might get to offset the additional competition — and the process for getting it — were among the key details not released Friday. O’Malley said he plans to make a bill public shortly before the session, which has prompted many legislators to juggle vacations and summer conference plans.

Todd Eberly, an assistant professor of political science, said O’Malley has a lot riding on the session’s outcome, given questions about his level of engagement in Maryland as he has become more active in national politics.

“When you’re the governor and you call a special session, the expectation is that it’s not going to waste everyone’s time,” Eberly said.

The plan under consideration, which has been championed by Prince George’s County Executive Rushern L. Baker III (D), would represent the largest expansion of gambling in Maryland since 2008, when voters statewide authorized five slots locations.

Any expansion passed during a special session would go on the ballot in November. O’Malley said a Prince George’s casino would not move forward without approval of county voters as well as state voters. Busch emphasized the importance of those provisions as he stood alongside O’Malley, other elected officials and labor leaders at the news conference.

“The ultimate decider of this issue is going to be the citizens of Maryland,” Busch said.

Similar gambling plans have enjoyed broad support in the Senate, putting the focus squarely on the House.

While leaders of both chambers have embraced table games to enhance existing slots facilities, plans for a Prince George’s casino have collapsed twice in recent months.

On the final night of this year’s regular legislative session, a Senate-approved bill stalled in the House amid brinksmanship between the two chambers over budget legislation.

A work group convened by O’Malley subsequently floated a similar plan that sunk when three House members who participated withheld their support, citing a concern about cutting taxes on casino owners so soon after raising them on six-figure earners. The five O’Malley appointees and three senators on the panel supported the plan.

Since then, O’Malley — who stood on the sidelines during the regular-session debate, calling gambling “a distraction” — has redoubled efforts to pass a bill.

Del. Justin D. Ross (D-Prince George’s), the No. 2 vote counter in the House, said he thinks reaching a majority in the House is achievable.

“I can’t sit here today and tell you we have 71 votes, but we don’t even have a bill,” said Ross, who supports a casino in his county. “As details become more clear and the work product is put forward, there’s going to be a path to victory.”

Ross noted that O’Malley and House leaders had pulled off difficult votes before, including legislation during this year’s regular session to legalize same-sex marriage.

Lawmakers also authorized Maryland’s slots program during a special session called by O’Malley in 2007, his first year in office. After days of arm-twisting, one of the two bills necessary to launch the program passed with 71 votes, the bare minimum needed.