Karen Bailey, a spokeswoman for Penn National, said Tuesday that if her company was solely interested in protecting Charles Town it wouldn't have proposed spending $500 million to build a casino at its Rosecroft Raceway in Prince George's. And she said the legislature treated her company unfairly when it gave tax breaks to other Maryland casinos but not to the one it owns in Perryville.

"We weren't even given a seat at the table, and the Prince George's site has all but been handed over to National Harbor with no intention of fair competition that would get the best deal for the State of Maryland," she said.

But before last month's special session, the company warned its shareholders of the risks its Charles Town casino faces from Maryland. And having won virtually no meaningful concessions from Maryland lawmakers, Penn National has every reason to spend heavily on its referendum fight.

"When you have $200 million in annual cash flow at risk, it is money that is well-spent," Beynon said.

Neither Penn National nor Cordish officials would comment on the reports of possible talks. Penn National officials did not return messages Wednesday seeking clarification of the company's position on the referendum in light of those reports.

If Penn National has compelling reasons to fight Maryland's gambling expansion, MGM and its allies have ample incentive to match it dollar for dollar. MGM is about three times bigger, with $7.8 billion in annual revenue.

Beynon said MGM, the largest owner of casinos in Las Vegas, needs to expand in other parts of the country. He said MGM was stung by a downturn in travel to Las Vegas during the recession.

"They need this. They need diversification," he said.

Estimates have varied as to how much revenue would be generated by a luxury casino at National Harbor. But there has been virtually unanimous agreement that the site would be a success in financial terms. Karmel said he could see it adding as much as $700 million in annual revenue for MGM.

MGM spokesman Gordon Absher emphasized the advantages a National Harbor casino would bring Maryland in jobs and education funding, the selling points in its ad campaign, but didn't deny that the company stands to make a lot of money at the site. Absher said National Harbor may offer the best blend of geographic, infrastructure and branding advantages MGM has ever seen.

"National Harbor speaks for itself," he said.

Both MGM and Caesars stand to gain from adding an attractive destination to further take advantage of their robust "players' club" networks.

Caesars, with $8.9 billion in annual revenue, is an industry leader in using its database to lure loyal customers to its different locations with enticing incentives. The company has said that table games would let it make the Baltimore casino more of a destination, with tie-ins to local events such as Ravens games.

Jan Jones Blackhurst, a Caesars spokeswoman, said table games could add an additional 500 jobs while helping to make Maryland's gambling industry more competitive. She said the company would be willing to invest an additional $35 million to $40 million the downtown casino, which she estimated would gain $80 million in annual revenues from the change.

"We're a much better product with table games like blackjack and craps and roulette," she said.

So far, there seems to be no limit to the spending on Question 7 as each side's bet prompts the other to raise the stakes.

"Our number seems to change every week, and it is based on the amount of dollars put up by the other side," MGM's Absher said.