The big money behind the Republican surge Tuesday came from a host of familiar billionaires.
Mega industrialists Charles and , powerful investor Paul Singer and casino magnate Sheldon Adelson all gave millions of dollars to support conservative candidates, helping the GOP take control of the Senate and add to their House majority.
But there's one name on the top 10 list of midterm donors most people won't recognize: Robert Mercer.
Better known as "Bob," Mercer is co-head of Renaissance Technologies, a secretive hedge fund firm that manages $25 billion using fast-trading computer programs from its headquarters in a quiet hamlet on Long Island.
Thanks both to looser campaign finance rules and his promotion to help lead one of the largest hedge funds in the world, Mercer has quietly become a major player in politics since 2010. He donated more than $8 million this election cycle alone, putting him behind only Singer as the second-largest Republican booster. And Mercer was fourth overall regardless of party after hedge fund manager-turned environmentalist Tom Steyer and former New York City mayor Michael Bloomberg, according to data compiled by the Center for Responsive Politics.