A plurality of Americans — almost two in five — say they view President Obama as most likely to last only a single term, a new poll found Monday.

A day before voters head to the polls to cast ballots in pivotal midterm elections, 39 percent of U.S. adults say Obama's presidency will end in 2012's elections.

Twenty-six percent said that Obama has performed well enough to earn a second term, while 33 percent were unsure, according to November's "60 Minutes"/Vanity Fair poll, released Monday.

While far from conclusive, the poll touches on the public's concern about Obama's work in office that undergirds Tuesday's elections.

Democrats have sought to avoid making Nov. 2 a referendum on their party's president, and have found success in races where they've been able to frame the vote about GOP candidates. But in many cases, Democrats on the campaign trail have largely fled from Obama and Democratic leaders in Congress.

The questions about Obama — the force of whose victory in 2008 led to a sense that he'd be difficult to defeat in 2012 — are a factor in the growing number of Republicans who have started to eye a challenge to the president in 2012.

The poll found that 10 percent of Democrats view Obama as a single-term president, and that 38 percent of independents saw him as a one-term president. (Fifteen percent said Obama deserved a second term.)

The poll, conducted Oct. 6-8, has a 3 percent margin of error.