According to a study conducted by Siena College in Loudonville, N.Y., Hoffman leads Owens 41 percent to 36 percent -- while 18 percent of likely voters said they were undecided.
The right-leaning New York congressional seat has become a sought-after prize for the Democrats, who sent Vice President Biden to campaign for Owens at a Monday morning rally in Watertown, N.Y.
GOP candidate Dede Scozzafava, who was criticized as too moderate by members of her own party, dropped out of the race over the weekend and endorsed Owens on Sunday.
But it remains unclear how much of an impact her endorsement will have, as many of her supporters are expected to drift toward Hoffman.
The new poll found that the number of undecided voters has doubled from 9 percent to 18 percent since Scozzafava announced her withdrawal from the race.
"Hoffman continues to demonstrate momentum, picking up six points since Scozzafava pulled out," Siena pollster Steven Greenberg said in a press release Monday. "It appears, however, that the majority of Scozzafava’s supporters have gone to neither Hoffman nor Owens, but rather into the undecided column, which has doubled since Scozzafava ended her candidacy."
The poll, which was conducted Nov. 1 by telephone calls, surveyed 606 likely voters. It had a margin of error of 4 percentage points.