It’s early, and other presidents had worse polling before coming back to win second terms, but this is still a bit of an eye-opener:

A CNN/Opinion Research Corporation survey released Thursday indicates that if the 2012 presidential election were held today, 47 percent of registered voters would back Obama, with an equal amount supporting an unnamed Republican challenger. Fifty-four percent of people questioned say Obama will lose if he runs for re-election in 2012, with 44 percent saying the president would win a second term.

Recall, however, that in 2008, Obama won with 53 percent of the vote, running as a “historic” candidate pushing a moderate message. It was inevitable that once the history was made and the reality of Obama — hyper-partisan, ultra-liberal — replaced the promise of Obama — post-partisan, moderate — that he was going to lose some ground.

To a large degree, 2012, as in all re-election campaigns, will be a referendum on the incumbent. Obama will need to defend his record — on everything from the deficit to unemployment to taxes — while the challenger will have an array of targets. In some sense it may be a reversal of 2008, when John McCain was essentially running as the incumbent– saddled with the economic failure and playing defense for the Bush administration. This time around it will be Obama on the defensive, given that his performance on nearly every domestic issue is rated unfavorably by the public. That might change, but it would require that Obama stop governing in ways that are antithetical to the concerns and values of the majority of the public. So far, there’s no indication that he intends to do that. Maybe he meant it when he said there were more important things to him than being re-elected. Perhaps a government takeover of a sixth of the economy was all he ever wanted to do.