That's part of the attraction for Baker, who has said a study commissioned by his administration shows that National Harbor would depend less on gambling by county residents and generate more revenue from out-of-state visitors than a rival site at Rosecroft Raceway. He has estimated that the site could add $69 million in annual revenue for the county and provide 5,000 permanent jobs.

The downside is that to raise the estimated $1 billion needed to build a luxury casino, National Harbor might have to persuade lawmakers to cut the existing 67 percent tax rate on slots machine proceeds by roughly half. That could be a tough sell just months after the state raised income taxes on about 14 percent of Maryland households.

The complex first opened in 2008, and four years later it offers visitors about 30 dining options, including the luxury Old Hickory Steakhouse, Bobby McKey's dueling piano bar and Nando's PERi-PERi, a specialist in Portuguese flame-broiled chicken. The 40 shops include the House of JonLei Atelier bridal salon, the upscale Tiki & Me pet accessories store and Peeps & Company, the first retail outlet in the nation devoted to the iconic marshmallow candy.

National Harbor's start goes back about 16 years, when the Peterson family acquired the 350-acre tract. It sat on an artificial cove created by the flooding of a former gravel pit, in the shadow of what was then a crumbling bridge with a reputation as the worst bottleneck on the Capital Beltway.

Jon Peterson said his father saw the potential, however. And once the old bridge was replaced and highway connections improved over the past decade, the location became National Harbor's biggest selling point.

The complex opened after more than a decade of wrangling with local residents and environmentalists. Some opponents feared it would contribute to the degradation of the river; others were suspicious that it would bring little but congestion to the middle-class neighborhoods nearby. Even before ground was broken, there were fears that the development was a stalking horse for a casino.

The Prince George's County government, however, has seen National Harbor as a source of revenue and jobs. Equally important has been the pride factor in a county that has existed in the shadow of Washington, Montgomery County and Northern Virginia. Residents had long been rankled by a lack of high-end stores and restaurants in the richest African-American majority county in the nation.

Baker said the early opposition to National Harbor has evaporated. "The county's taken to it like gangbusters," he said.

Del. Aisha Braveboy, a Democrat who represents a nearby district, agreed that county residents take pride in the destination. But she is one of several local elected officials who do not share the view that a casino would make it even better.

"For years, National Harbor has been promoted as a family-friendly destination," she said. "We need to keep that brand for National Harbor. I don't think that putting a casino down there is going to lend itself to maintaining that brand."

But Del. Jay Walker, a Democrat from the district that includes National Harbor, said that if voters approve, he's in favor of allowing a casino. "I think it would raise a tremendous amount of money for the state of Maryland in terms of capturing [out-of-state] revenue."

National Harbor's owners say they are not sweating the outcome of O'Malley's gambling task force or a possible legislative special session. Peterson said that if the General Assembly doesn't pass a bill putting the casino question on this year's ballot, the site might still be available in 2014, the next time Marylanders could vote on the issue. Or it might not.

"We've got a lot of things we can move on and do," he said. "We know that good things are going to come to National Harbor."

Baltimore Sun reporter Annie Linskey contributed to this article.