WASHINGTON -- Sen. Scott Brown and his Democratic challenger are nearly tied in the race for a Massachusetts Senate seat, according to a poll released Wednesday night. This new result suggests that relentlessly negative news coverage over allegations that Warren embellished her biography have had little impact on a race that has remained deadlocked for months.The new poll, conducted by the Suffolk University Political Research Center and sponsored by Boston television station 7News, gave Brown a one percentage point edge over Warren (48 percent to 47 percent), with just 5 percent undecided.