It's pretty much an iron rule of politics - the longer a new president's coattails the worse his losses will be in his first mid-term election. This is even more true when economic conditions are bad.
Let's look at the last three two-term presidents. Reagan was elected after years of high inflation and unemployment. The country was just slipping into a recession in 1980 and the economy was still in bad shape in 1982. Republicans took a beating in the election.
In 1992 Clinton was elected during a recession. His margin or victory and his majority in Congress were nearly identical to Obama's. In the 1994 election he lost both houses of Congress.
George W. Bush is the exception. He actually made a slight gain in 2002. There were a few mitigating factors here. He was elected without coattails in 2000 and the country was at war in 2002. Bush's post 9/11 approval rating was still high.
This history is important for Republicans trying to chart a new path. They are being told that Reaganism has run its course and they need to find new ideals or risk a long time in the wilderness. History says that this is not so. The same thing was said about Reaganism in 1992 but limited government Republicans were able to take Congress back in 1994.
Obama himself is proof that you don't need new ideas. He ran on the New Deal. If he can repackage FDR 76 years later then Republicans can resurrect Reagan. It's not like Bush was a Reagan believer. He was a believer in big government solutions to everything. He called it compassionate conservatism. This was a problem for him when government inevitably failed (Katrina).
Republicans can spend the next two years distancing themselves from Bush's domestic policies.
In the meantime, it is unlikely that Obama will magically fix the economy. Economic recovery takes time even under a mild recession. If Obama listens to his supporters, especially unions, then he will make the recession much worse, guaranteeing a Republican sweep in two years.
Of course, history also has Reagan and Clinton recovering from their mid-term losses and being reelected during an economic boom. On the other hand, Carter had back to back recessions and lost. George H. W. Bush also lost in a recession.
History's final lesson - even talented charismatic presidents get low approval ratings during an extended recession. This happened to both Reagan and Clinton. If Obama manages to screw the economy up badly enough then the country will throw him out.