Over the weekend, a poll from Western New England University gave Warren a 50-44 percent lead, while a survey from Democratic-leaning Public Policy Polling found a 48-46 percent advantage.

Warren's lead comes despite voters giving Brown significant credit; pluralities say the incumbent is running a better campaign, would be more independent in the Senate and better represents the interests of the state. Moreover, when voters were asked to describe Brown, they most frequently used the phrases "Republican," "honest" and "independent" — versus "smart," "consumer protection" and "liar" for Warren. That's indication that the Democrat was potentially bruised by her claim of Native American heritage.

But Warren leads Brown 49-42 percent on the crucial question of who would better represent middle-class families — and, of course, in the overall race.

Warren and Brown are scheduled for the first of four debates this Thursday at the CBS affiliate in Boston.