ANNAPOLIS -- Maryland voters will decide in November if they want to add a sixth casino in Prince George's County and table games such as blackjack at current slots parlors.

Gov. Martin O'Malley signed legislation allowing the state's gambling industry to expand, with millions of dollars in tax breaks for casino owners, on Wednesday morning, less than 10 hours after lawmakers passed the bill early in a special session that lasted until nearly 12:30 a.m.

It's the second time in four years that gambling will appear on ballots in Maryland, and the vote will be critical in Prince George's County, where residents could block efforts to bring a casino to the southern portion of the county even if voters statewide approve the governor's plan.

Senate President Thomas V. Mike Miller Jr., D-Calvert and Prince George's, and County Executive Rushern Baker said they were confident voters in the county would approve the casino plans.

Prince George's could collect $40 million to $60 million annually in taxes from a resort casino at National Harbor, Baker's preferred destination.

"I think [voters will] look at that and make a decision to go forward with this," he said.

Nearly 60 percent of Prince George's voters approved slots in 2008. Ministers in the county say that won't happen again this year.

"There are literally tens of thousands, perhaps hundreds of thousands of people in Prince George's County that are fully prepared to say no," said Rev. Jonathan Weaver, pastor of Greater Mt. Nebo African Methodist Episcopal Church.

Comptroller Peter Franchot said the fight against tax breaks for influential casino owners is just beginning.

"This is a question of whether we will allow the national gambling industry to control our political process from the backrooms of Annapolis, or whether we will take a stand for open, transparent and progressive government," he said.

The gambling bill leaves open the possibility a Prince George's site could be approved at Rosecroft Raceway in Fort Washington, but Baker pledged to throw his support behind a bid by MGM Resorts International and the Peterson Cos. to build at National Harbor.

But Miller, who called National Harbor an "ideal site," said Rosecroft is still in the mix.

"I wish there was some way to share the machines quite frankly, because they're both ideal sites, and we'd also be able to find some way to keep horse racing alive in Prince George's County," Miller said.