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…

“If we have third-party or independent candidates, it is possible for Obama to have a low- to mid-40s approval rating and win,” Mr. Sabato said. “Nixon ‘68 and Clinton ‘92 each got 43 percent of the vote. [Woodrow] Wilson and [Abraham] Lincoln [in 1912 and 1860, respectively] received around 40 percent of the vote in multicandidate fields. The structure of the ballot will matter enormously, depending on whether we have additional candidates and who they are.”…

“Presidential approval one full year out is not helpful in determining what will occur in November 2012,” Mr. Sabato said. “The old rule used to be that a president had to have approval in the 50 percent range at election time to get a second term. But George W. Bush had 48 percent in early November 2004 and still won. His superior financing and organization pulled him over the finish line against John Kerry.”