REMEMBER THE POT OF GOLD promised by Maryland’s gambling lobby less than a decade ago? Slot machines, they said, would deliver a practically bottomless bounty — $700 million or $800 million annually that casinos, once legalized, would pour into the public coffers, providing a panacea for the state’s budget deficit; paying for school upgrades; and rescuing the slumping horse racing industry. Why, the slots crowd enthused, gambling would even prevent sprawl by saving horse farms from predatory developers!

More than three years after voters approved slots, reality has punctured all those promises. Under current projections, recently downsized by legislative analysts, the best that can be hoped for is $475 million in tax revenue from slots — over the next five years. Not exactly a cure-all in the context of the $30 billion in revenue the state will collect this year alone.

Nonetheless, advocates are pushing an expansion in gambling, suggesting it will solve a new problem: the woeful shortage of good health care in Prince George’s County. Only by plonking down a gigantic casino at Rosecroft Raceway, just south of the District in Fort Washington, would tens of millions of dollars in tax revenue materialize — enough to fund a badly needed new county hospital.

We were under the impression that hospitals got built in Maryland even before gambling was legalized at referendum in late 2008. But that hasn’t stopped Penn National Gaming, Rosecroft’s latest owner, and its allies in Annapolis, from promising that slots at Rosecroft — thousands of them — would yield a windfall sufficient to build a hospital.

A casino at Rosecroft, Penn National claims, would produce better than $400 million annually in tax revenues for Maryland, including $40 million for Prince George’s. Thomas V. “Mike” Miller, the state Senate president who has long been gambling’s champion, has seized on such rosy numbers to suggest a casino — and only a casino — would get the hospital built.

That argument, based on projections that Penn National has every reason to inflate, wouldn’t gain much traction in flush times, when lawmakers seem somehow more able to remember the social ills that come in gambling’s wake. In lean times, it gets a better hearing, judging from the current waffling from state and county politicians, including some who have opposed gambling in the past.

County Executive Rushern Baker (D) and Prince George’s lawmakers should remember the unmet promises of the past. Greed, not health care, impels the gaming industry, which for years has pumped hundreds of thousands in campaign contributions into the accounts of pliant state legislators.

There is nothing new about hitching a casino to the aging, failing track at Rosecroft — the idea’s been around since the ’90s. Officials resisted it for good reasons, knowing that it would exact a heavy price, particularly on poor people who live nearby. Now, given Prince George’s determination to overcome a reputation for tawdriness and corruption, there is even more reason to refuse to brand the county as the Washington area’s gambling mecca.