The Field Poll found a 4-percentage point spread, with 43 percent of those surveyed saying they support Feinstein while 39 percent say they do not, The Sacramento Bee reported. At this point in previous election cycles, Feinstein's margin of support has ranged from 19 to 29 points.
Forty-six percent said they approve of her performance as senator while 31 percent disapprove and 23 percent have no opinion one way or the other.
Feinstein, a former mayor of San Francisco, was first elected to the Senate in 1992, winning a special election for the seat left vacant when Republican Pete Wilson became governor.
Bill Carrick, who has long been Feinstein's political consultant, said she has been hurt by factors beyond her control.
"It's tough economic times," Carrick told the Bee. "In this environment, I think it's good that so many people express more positive feelings about her than negative."