According to campaign finance documents analyzed by the Wall Street Journal and filed on Thursday, the Adelsons contributed $23 million to American Crossroads, the super PAC launched by Karl Rove, and $10 million to the leading super PAC backing Romney, Restore our Future, adding up to a $33 million effort in the final stretch of the campaign.
The Wall Street Journal writes that "combined, the donations represent the largest political contribution of the entire 2012 election and among the biggest in modern campaign-finance history."
The campaign finance documents also reveal that American Crossroads, which also played in some Senate races, received $37 million in donations in the final three weeks of the campaign. That includes a $4 million donation from the second-highest Republican donor of the cycle, Texas billionaire Harold Simmons.
Adelson, a Casino magnate worth billions, was, based on available records, one of the largest Republican donors this past election cycle.
Though Republicans were unable to take the White House or the Senate majority this cycle, Adelson said he's not deterred from spending an even larger sum on future elections.
"I happen to be in a unique business where winning and losing is the basis of the entire business," he said. "So I don't cry when I lose. There's always a new hand coming up."