Sen. Ben Nelson (D-Neb.) would start his 2012 reelection race in a weak position if Nebraska Attorney General Jon Bruning wins the primary, according to a new poll.

The survey by Republican firm Magellan Strategies put Nelson 6 points behind Bruning in a general election. But pitted against Don Stenberg, another Republican in the race, Nelson is in a statistical tie. He bests Nebraska state Sen. Deb Fischer (R) by 6 points.

Another cause for concern for Nelson, who has not yet announced whether he will seek reelection, is his 36 percent approval rating, which dwarfs the 51 percent who disapprove. All of the Republican candidates — except Bruning — also have more voters who disapprove than approve.

But the Republicans all have higher rates of voters who haven't yet made up their minds than Nelson, who is finishing up his second term in the Senate.

Nelson won his 2006 reelection by almost 30 points over Republican Pete Ricketts, but his 2012 fate is less certain, and Republicans see a major opportunity to unseat him.

The Magellan poll of 645 Nebraska voters was conducted Nov. 20-21 using automated telephone interviews, and had a margin of error of plus or minus 3.9 percentage points.