A new poll shows US Senator Scott Brown with a lead over Elizabeth Warren, a break from a string of four previous polls that showed Warren leading the race.

The new University of Massachusetts Lowell/Boston Herald telephone poll of 524 voters, released Wednesday night, showed Brown leading 49 percent to 45 percent among those deemed likely to vote.

The survey was conducted from Sept. 13 to 17 and had a margin of error of plus or minus 5 percentage points. The organization’s previous poll, taken in December, showed Warren leading by 7 percentage points.

The lead in the race for the US Senate has swung back and forth for most of the year. With the release of each poll, both campaigns have said they expect the fluctuations to continue until Election Day in what has been one of the nation’s most competitive Senate races.


Warren — a Democrat challenging Brown, a Republican — had led in four consecutive polls released this week, by a margin of between 2 to 6 percentage points.

The most recent of the polls showing Warren ahead was conducted over roughly the same period as the UMass poll, from Saturday through Monday, by WBUR/MassINC Polling Group and was released Wednesday morning. It showed Warren leading 45 percent to 40 percent among 507 likely voters.

Warren seems to have benefited more from her party’s convention than Brown. She gave a prime-time address two weeks ago at the Democratic National Convention in Charlotte, while Brown kept a low profile at the Republican National Convention in Tampa a week earlier. Democrats hold a 3-to-1 advantage in voter registration in Massachusetts, and Brown is following the tradition of many Republicans who try to take the focus off party affiliation.

Brown had a lead in one public poll taken just before the conventions.

The candidates are scheduled to begin the first of four televised debates on WBZ-TV (Channel 4) at 7 p.m. Thursday.

The face-to-face interactions could prove pivotal. The UMass poll released Wednesday night showed that 29 percent of Brown voters were open to changing their minds, as were 19 percent of Warren voters.