A study issued Wednesday says an expansion of casino gambling in Maryland will not produce the kind of revenue supporters say it will.

About 45 percent of the revenue promised from adding a casino in Prince George’s County and table games at Maryland casinos is existing gaming revenue, according to the study issued by the Maryland Public Policy Institute, a nonpartisan think tank based in Rockville. Supporters of Question 7, the gambling expansion referendum, on the other hand, have said an expansion would generate $199 million annually for Maryland schools.

“This objective analysis debunks many of the most attractive arguments for Question 7, particularly that a ‘Yes’ vote will significantly improve state revenues and benefit Maryland public education,” Christopher Summers, president of the Maryland Public Policy Institute, said in a statement.

Cutting casino tax rates for casino operators to compensate them for lost business from a Prince George’s County casino will reduce the amount of money a casino expansion would contribute for education funding, the report said.

The report comes as proponents and opponents of expanding gambling in Maryland spend millions to sway voters on Question 7 ahead of the Nov. 6 referendum.

On Monday, supporters of expanded gambling in Maryland released a report saying state residents will spend between $1.1 billion and $1.5 billion at Penn National Gaming’s casino in Charles Town, W. Va. The report did not tally how much is lost to casinos in Delaware and Pennsylvania.