President Barack Obama is virtually tied in potential re-election match-ups with four Republican presidential candidates in a new Gallup survey.

Among registered voters, the president leads Minnesota Rep. Michele Bachmann by 4 percentage points and Texas Rep. Ron Paul by 2 points. He is tied with Texas Gov. Rick Perry and trails former Massachusetts Gov. Mitt Romney by 2 points. The poll's margin of error is plus or minus 4 percentage points.

Republicans most strongly favor Perry and Romney in a race against Obama, with 92 and 91 percent saying they would vote for those two candidates. But only 86 percent of Republicans say they would vote for Bachmann, and only 82 percent say they would vote for Paul. Independents also favor Romney, Perry and Paul against Obama, but slightly favor the president when he's matched against Bachmann. The president's approval rating continues to hover around 40 percent--a dangerously low total, according to Gallup's calculations.

"This is below the rating that any of the six incumbent presidents re-elected since Eisenhower has had at the time of the presidential election," Gallup writes.

But Obama has more than a year before his re-election race. Gallup notes that in August of the year prior to their re-election campaigns, Ronald Reagan and Bill Clinton were each below the 50 percent approval mark.

Additionally, the candidates in the Republican field have yet to capture many voters' attention. "More Americans at the moment say they would vote for Obama than approve of the job he is doing--perhaps a reflection of the continuing lack of a strong front-runner on the Republican side," Gallup writes.