It's difficult to win re-election in bad economic times. Just ask Bush 41 and Jimmy Carter. It's impossible to win re-election when you don't have a consistent winning message. Right now, the Obama campaign is lurching about from one message to another, changing course each week. This week, the message is "I killed Osama Bin Laden (and maybe Mitt Romney wouldn't have)." Last week, the message was "I will keep student loan interest rates low (and maybe Mitt Romney won't)." The week before, "I'm for the Buffet rule (and Mitt Romney is a millionaire)." Then there was, "I will protect a woman's right to free contraception (and Mitt Romney wants to keep women barefoot and pregnant)."
To win, Obama has to find a message that resonates with voters and then stick to it. He could try: "I'll raise taxes", but that didn't work out too well for Walter Mondale against Reagan. Or "My opponent is an extremist", but that didn't work for Jimmy Carter against Reagan.
When Robert Gibbs was asked on Meet the Press what "big idea" Obama would campaign on, he said:
Well, look, the biggest idea that we're running on is to continue moving in the right direction of fixing this economy.
Really, that's their big idea. Only 32% of voters (RCP average) think the country is moving in the "right direction", according to current polls. Even elements of the Democratic base don't buy this contention. If the Obama campaign chooses to make "stay the course" the rationale for re-election, Romney will win in a land-slide. Just ask George H.W. Bush.