A new WBUR/Mass Inc. survey has Scott Brown edging ahead of Elizabeth Warren by a 47% to 43% margin. With “leaners” included the margin is 48% to 45%, with 5% undecided.

The poll also measured the Presidential race with Barack Obama leading Mitt Romney by a 52% to 36% margin. While that may appear to be a substantial lead it is down substantially from the pre-debate Suffolk poll that had Barack Obama with a 27% lead. We had discussed the “Romney drag” on Scott Brown in an earlier post, but the Romney debate victory looks like it may be having a positive impact on Brown’s candidacy. What the good Lord giveth, the good Lord taketh away.

So what are the numbers under the hood? I have focused, in this race, on two key numbers. The independent vote, in this survey, has Brown ahead by 22% in this demographic. He needs a little bit more to be comfortable. With all the discussion of the impact of Obama in this race the vote by Party is critical to Elizabeth Warren. In this survey Warren is only getting 72% of the Democratic vote, which is the key to the Brown lead here. Brown is getting 21% of Democrats here, while commanding 94% of Republicans. Warren needs to drive her number up with Democrats, which has been a key focus of her campaign. The Obama slippage may be having some impact on her.

The race remains tight, and fluid. You can expect Warren to continue her effort to pry Democratic voters away from Scott Brown. That means a wee bit more negativity coming in the days to come. Great race.