Berg leads Heitkamp, the former state attorney general, 51-44 in the poll by Forum Communications Co., which owns multiple newspapers in North Dakota.
Independent polling is in short supply in North Dakota, where state law bars firms from using automated telephone surveys, which are less expensive to conduct. Republicans see retiring Sen. Kent Conrad’s (D-N.D.) seat as one of their strongest pickup opportunities for 2012.
The poll of 500 likely primary voters was conducted May 3-8 and had a margin of error of plus or minus 4.3 percentage points.
The Hill rates this race a toss-up.