Republicans remain confident that Berg, a Tea Party-backed fiscal conservative, will clinch Conrad's seat and give them one of four Democratic seats they need to flip to take back control of the Senate, if President Obama is reelected. A poll by Democratic pollster Geoff Garin in August — before Heitkamp entered the race — showed Berg with a four-point lead over a generic Democrat.

Tuesday's poll also revealed some harrowing news for Obama, who trails Mitt Romney by 14 points in North Dakota. While Obama and his allies aren't counting on a win in North Dakota — he lost there to Sen. John McCainJohn Sidney McCainSenate's defense authorization would set cyber doctrine Senate Dems hold floor talk-a-thon against latest ObamaCare repeal bill Overnight Defense: Senate passes 0B defense bill | 3,000 US troops heading to Afghanistan | Two more Navy officials fired over ship collisions MORE (R-Ariz.) by eight points in 2008 — Romney's wide margin over Obama is a cause for concern that having Obama's name on the ballot drags down other Democrats.

The poll of 600 likely voters was conducted Nov. 12-16 using live telephone interviews. The margin of error was plus or minus 4 percentage points.