President George W. Bush is widely unpopular, even with a fair number of Republicans. Barack Obama won by running against George W. Bush. Voters rejected McCain as more of Bush and elected Obama.
That scenario won't work for Obama in 2012. As former Prime Minister Harold Wilson famously said, "A week is a long time in politics." If a week is a long time, four years are an eternity. In 2012 nobody will remember how much they wanted to get rid of W.
In 2012 Obama will have to run on his record. The 2012 election will inevitably be a referendum on Obama's performance in the first term. A majority of Americans will need to be pleased with his performance if he is to be reelected. His Republican challenger will be the one offering people "change." Obama will be the one defending the status quo.
As Obama decides what to do in the coming months and years, he needs to keep that truth firmly in mind. If he fails to do so, historians will view him as another Jimmy Carter; a well-intentioned loser who could get elected given favorable circumstances but could not perform once in office.