President Obama beats all Republican challengers tested against him in a series of hypothetical 2012 match-ups, a new poll found Wednesday.

Obama enjoys leads over former Massachusetts Gov. Mitt Romney (R), former Alaska Gov. Sarah Palin (R) and Sen. John Thune (R-S.D.) by varying margins, according to an NBC News/Wall Street Journal poll released Wednesday evening. 

The president maintains a small lead within the margin of error over a generic GOP opponent. Forty-two percent of U.S. adults said that they would probably vote to reelect Obama in 2012, while 39 percent said they'd prefer a Republican. Six percent were unsure, while 10 percent said it depended on the challenger to Obama.

But Obama performs even better against Romney, Palin and Thune — three Republicans thought to be interested in challenging Obama for control of the White House in two years.

Forty-seven percent would vote for Obama if Romney were the nominee, while 40 percent would vote for the former Massachusetts governor, the poll found.

Obama beats Palin, the 2008 Republican vice presidential nominee, 55 percent to 33.

The president also leads Thune, 47 percent to 27, though a much larger number of respondents to that hypothetical (17 percent) said they were not sure, reflecting that Thune is relatively unknown as a national Republican at this point.

A number of would-be GOP challengers to Obama went untested in the poll. The survey did not evaluate how former Arkansas Gov. Mike Huckabee, Minnesota Gov. Tim Pawlenty, former House Speaker Newt Gingrich (R-Ga.), Sen. Jim DeMint (R-S.C.), Rep. Mike Pence (R-Ind.) or Rep. Ron Paul (R-Texas) would fare against Obama.