I think there is another dynamic at work here. Wall Street, the banksters and a lot of corporations and billionaires sank a whole bunch of money into conservative PACs in support of Romney. Now they feel that they were led down the primrose path and given promises that were not kept. They will not stand idly by watching Boehner and Cantor try to stiff this president for four more years while this economy continues to stagnate. Even if the fundamentalists on the Right don't see a mandate (hey, they didn't see the polls either!), businessmen and bankers are far more pragmatic as a rule. They see that Romney put forward an agenda that was rejected by the people. They're not going to keep throwing good money after bad. Boehner, and the rest of the Republican leadership are going to get some feedback from Big Money. And it's not going to be good news. They will be "encouraged" to compromise.
Besides, this election Wall Street and the banksters bailed on Obama and threw their support over to Romney. Now they see they have no punches on Obama's dance card. In other words, he owes them nothing. Also, the biggest support he got from the American people on the campaign trail was for the idea of the rich paying a little more in taxes as part of a balanced deficit reduction deal and taking the weight off the backs of the middle class. He's got no reason to cut any slack on that issue.