The Vegas-based company hoping to build a resort casino at National Harbor put up another $3 million to back a Maryland ballot question on expanding gambling, nearly matching the sum that Penn National Gaming has donated to defeat the measure.

MGM Resorts International wrote a check for $2.9 million on Friday, bringing to $5.4 million the amount they've dedicated so far to passing "Question 7" in November. The competition, Penn National Gaming, has donated $5.5 million to an organization aimed at defeating the ballot question.

For context: In the 2010 gubernatorial election the spending on both sides reached $17 million. (Gov. Martin O'Malley spent $10 million. Former Gov. Robert Ehrlich spent $7 million.)

The rapid pace of spending has turned heads -- the ballot groups on gambling only formed late last month after the General Assembly approved legislation authorizing a sixth casino, to be located in Prince George's County, and table games like poker at all locations. Some casino owners will get tax breaks to compensate them for the added competition.

Voters must ratify the legislation on November's ballot before it would go into effect. 

MGM wants to build and operate the new casino. Their ad campaign focuses on the additional money that the gambling expansion would bring to the state coffers.

Penn National, which opposes, feels that it's casino in Perryville was treated unfairly in by the General Assembly. It is the only one without a guaranteed tax break. Also, the company has said in SEC filings that its casino in West Virginia could be hurt by a new facility in Prince George's County.