Groups with a stake in Maryland's referendum on expanded gambling spent more than $35 a vote during the 2012 campaign, according to an analysis by WTOP.

Unofficial results from the Maryland Board of Elections show that 2,479,262 people cast a vote on Question 7, which asked residents whether they favored the introduction of table games to the state and the addition of a sixth casino in Prince George's County.

The measure narrowly passed by a margin of 51.9 percent to 48.1 percent. But before the matter was decided, opponents and supporters undertook enormous advertising efforts to sway voters.

Casino operators that stood to benefit—including MGM Resorts International, CBAC Gaming LLC, and The Peterson Companies—were pitted against casinos in neighboring states, particularly Penn National Gaming's Hollywood Casino at Charles Town Races.

Question 7 was just one of several expensive, down-ticket races in the region. The senate campaign in neighboring Virginia saw spending to the tune of $20 a vote, the station found.

Read the full story from WTOP.