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 McCainOvernight Cybersecurity: Obama commutes Chelsea Manning's sentence | A malware mystery Overnight Defense: Obama commutes Manning's sentence | Boeing sees 'progress' on Air Force One costs | McCain's 0B defense budget McCain: Leak of Trump dossier ‘totally wrong’ 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.