MGM Resorts is putting down $2.3 million to convince voters to let the gambling and hotel giant open a new casino at National Harbor.

In an effort to win over voters, the Las Vegas casino operator recently gave the money to For Maryland Jobs and Schools, a group supporting the ballot measure that would legalize gambling in Prince George's County and table games statewide, a campaign finance report shows.

Developers at National Harbor announced in June that MGM would invest at least $800 million to build and operate a casino there, assuming voters approve an expansion of Maryland gambling in November. The casino would include 4,000 slot machines and 250 table games, as well as a luxury hotel with shops and restaurants.

The Md. ballot question on gambling
Do you favor the expansion of commercial gaming in the state of Maryland for the primary purpose of raising revenue for education, which would include the authorization of video lottery operation licensees to operate "table games" as defined by law; increasing from 15,000 to 16,500 the maximum number of video lottery terminals that may be operated in the state; increasing from five to six the maximum number of video lottery operation licenses that may be awarded in the state; and allowing a video lottery facility to operate in Prince George's County?

Rosecroft Raceway in Fort Washington also would be able to bid for a Prince George's casino under the terms of legislation signed by Gov. Martin O'Malley earlier this month.

MGM representatives could not be reached for comment.

The money is part of what many expect to be a heated and expensive campaign by both sides of the issue in the weeks leading to the Nov. 6 election.

Advocates of expanded gambling say a National Harbor casino will bring much-needed jobs and tax revenues to the cash-strapped county and state. State analysts have predicted the planned casino and resort could bring in at least $100 million more a year.

Prince George's County Executive Rushern Baker plans to continue to fight for its passage between now and November, spokesman Scott Peterson said.

But others have argued that a sixth casino will take business away from the state's other casinos, such as Maryland Live! at Arundel Mills mall, which opened in June and is 33 miles away.

Penn National Gaming, the owner of Rosecroft Raceway in Fort Washington, has expressed concerns that a National Harbor casino could hurt its casino in Charles Town, W.Va., as well as its business at Rosecroft.

Penn National did not return calls for comment.

Staff writer Ben Giles contributed to this article.