With Sunday marking the one-year countdown to Election Day 2012 and his approval rating stuck in the low 40s, President Obama will have to defy American electoral history if he is to win re-election.

At 43 percent approval in a Gallup poll conducted Oct. 28-30, Mr. Obama recently referred to himself as an “underdog” — with good reason. Of all the presidents since World War II whose job-approval scores were lower than 50 percent one year before Election Day, only one went on to win a second term.

That was President Nixon, whose job approval stood at 49 percent in November 1971. He rebounded to defeat Democrat George McGovern in a landslide in 1972.

Mr. Obama does have some advantages. He is still a formidable fundraiser, having amassed more than $150 million for his campaign and the Democratic National Committee this year...