DON’T GET COCKY: Betting Markets Have Flipped to GOP Control of the Senate. After two months of bettors favoring the Democrats to retain control of the Senate, the markets flipped this week, and bettors now give Republicans a better than 60 percent chance of taking the Senate. Five Thirty Eight’s model still favors the Democrats (it gives them a 58 percent chance to retain Senate control), but Nate Silver says he personally considers it a toss-up.