Kimball Political Consulting, a Republican-oriented firm, reported Friday that 49 percent of likely voters said they would go for Brown, while 47 percent picked Warren,
The survey also showed Brown with an edge in the favorability rating. While 55 percent said they have a favorable view of Brown and only 38 percent a negative one, 49 percent viewed Warren favorably and 45 percent unfavorably.
A Boston Globe poll last Monday gave Brown a 2-point edge. But a Suffolk University/News 7 poll Tuesday put Warren ahead by 7 points.
Kimball surveyed 761 likely voters on Wednesday and Thursday. The poll's margin of error is 3.48 points.
Brown won a special election for the seat held by the late Edward Kennedy, becoming the first Republican in decades to win a Senate race in Massachusetts. Warren, who became known as a consumer advocate in the Obama administration, has recently been teaching at Harvard Law School.