The odds are not great for the GOP given that there is very little chance that Obama won't be at the top of the Democratic ticket.
Defeating an incumbent president requires an exceptional candidate.
--Julian E. Zelizer
Several factors seem necessary to prevent a president from being re-elected. The first is a strong primary challenge that weakens support for the president within his own party. In Ford's case, Ronald Reagan mounted an unexpectedly strong campaign by attacking the president for staying too close to the center of the political spectrum.
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In 1980, Sen. Edward Kennedy did the same to Jimmy Carter, charging that the president had embraced Republican ideas such as deficit reduction and that he sold out the liberal base of the party. President George H.W. Bush struggled against Patrick Buchanan, who rallied the right wing in the primaries. Before Truman and LBJ dropped out, both of them faced primary challenges.
In 2012, a strong primary challenge to Obama is unlikely. Most prominent Democrats have refrained from even exploring this possibility, despite discontent on the left. If there is a challenge, it is likely to come from someone like Rep. Dennis Kucinich of Ohio, who does not have the stature to cause significant problems for the president.
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The second factor in the defeat of incumbents is a bad economy. Here Obama has reason to worry.
Both Gerald Ford and Jimmy Carter governed in an era of stagflation. The nation suffered from unemployment and inflation at the same time (which economists had said was impossible). In Carter's case, the nation had also been shocked by a second oil embargo by OPEC in 1979.
When George H.W. Bush set off to run in 1992, a recession was making Americans worry about their finances and job security. In all three cases, their opponents were able to position themselves as candidates who would revive the economy.
This time around, the economy will probably still be in bad shape. That said, with an improving set of statistics on unemployment and a rising stock market, there is evidence that the economy is moving in the right direction.
If this continues, even if conditions are far from perfect, many Americans will be left with the impression that the economy is on the mend. Obama will doubtless receive some credit for his policies. This will make it more difficult for the GOP, especially since the downturn began under George W. Bush.
http://edition.cnn.com/2011/OPINION/03/07/zelizer.obama.reelection/#