Wayne K. Curry. (Kevin Clark — The Washington Post)

Curry said he would seek funding from business and community organizations to promote the prospect of a new Prince George’s casino, which would be allowed under Question 7. The facility, he said, would be “a unique attraction for the tens of millions of people who visit our nation’s capital each year.”

It’s unclear how much impact Curry’s involvement will have in an already costly debate that is playing out in television ads across the state. He pledged to provide “some clarity and straight talk” on the measure, which has been championed by the current Prince George’s executive, Rushern L. Baker III (D).

Expanded gambling supporters have already given $23 million to a separate ballot-issue committee fighting for passage of Question 7, which would also allow Las Vegas-style table games at Maryland’s five existing slots casinos.

The leading opponent of the measure, Penn National Gaming, has given more than $25 million to a committee trying to defeat the plan.

Curry said $500,000 in initial funding for his group would come from the Peterson Cos., the developer of National Harbor, a commitment confirmed by a spokeswoman for the company.

National Harbor is widely considered the most likely site of a Prince George’s casino if Question 7 passes. Peterson has separately contributed $1.3 million to the other pro-expansion committee.

Other contributions to that committee include $18.2 million from MGM Resorts, which is angling to build the casino at National Harbor; and $3.5 million from a group led by Caesars Entertainment, which plans to open a Baltimore casino in 2014.

Penn, which is opposing the plan, operates a large-scale casino in Charles Town, W.Va., that analysts say would take a hit if another major casino opens in Maryland.

“It has become clear to me that this unprecedented blitz of advertising from a West Virginia casino has muddied the choice facing voters, and supporters of Question 7 need to come together to do everything we can to fight to bring Maryland (gambling) dollars back to Maryland,” Curry said.