Maryland Gov. Martin O'Malley (J. Scott Applewhite/Associated Press)

“Perhaps some future governor will want to wrestle with this issue again,” O’Malley (D), whose second term ends in January 2015, said during an appearance on WTOP’s “Ask the Governor.”

O’Malley also used the talk show to criticize Penn National Gaming for spending so heavily to try to defeat the gambling-expansion plan on the ballot.

So far, Penn has ponied up more than $18 million in an effort to derail Question 7, which would allow a new casino in Prince George’s, as well as Las Vegas-style table games at Maryland’s five previously authorized slots sites.

The legislature authorized putting the question to voters during a special session in August called by O’Malley, who said at the time that he wanted to put the divisive issue of gambling behind him.

On WTOP, O’Malley noted that Penn has spent far more in opposition to the expansion plan than the $2 million it spent in favor of a referendum in 2008 that launched Maryland’s slots program. At the time, Penn was interested in breaking into Maryland’s market. In fall 2010, it opened the state’s first casino in Cecil County.

Now, O’Malley said, Penn is “trying to protect its market in Charles Town,” a reference to a much larger facility the company operates in West Virginia.

Analysts say Penn’s Charles Town casino would take a financial hit if another large-scale casino opens 70 miles away in Prince George’s.

Penn officials have denied that they are being motivated by a desire to protect Charles Town, citing their stated willingness to build a $500 million casino at Rosecroft Raceway, a horse track in Prince George’s.

The gambling expansion plan calls for competitive bids from locations in a swath of Prince George’s that includes both Rosecroft and National Harbor, the 300-acre mini-city on the Potomac River.

Penn has argued that the deck is stacked against them, however, because Prince George’s County Executive Rushern L. Banker III (D) and others have championed National Harbor as a casino site.

Penn has reported spending more than any other company with a stake in the outcome of Question 7.

MGM Resorts, a company angling to build a casino at National Harbor, has contributed $11.4 million to a ballot-issue committee campaigning for the expansion plan.

According to updated reports, the Peterson Cos., developer of National Harbor, has kicked in $1.3 million, while a group led by Caesars Entertainment has contributed $3.4 million.

Caesars plans to open a Harrah’s-brand casino in Baltimore in 2014.