A new poll finds Senator Scott Brown leading his Democratic challenger, Elizabeth Warren, by 8 percentage points. The poll was released Sunday by the Western New England University Polling Institute in partnership with The Republican newspaper of Springfield and MassLive.com. Of 527 registered voters asked how they would vote if the election for the Senate seat were held today, 49 percent were for Brown, 41 percent for Warren, and 10 percent were undecided. The poll has a 4.3 percent margin of error. It was one of several recent polls that place the incumbent ahead of Warren. The survey was conducted between Feb. 23 and March 1.