Democratic challenger Elizabeth Warren leads Republican incumbent Scott Brown in the latest poll of their US Senate race.

A WBUR survey released today had Warren at 48 percent and Brown at 43 percent, a 5 percent gap that exceeds the poll’s 4.4 percentage-point margin of error.

It was a reversal of a similar survey earlier this month, which found Brown ahead by 4 percentage points.

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“The last poll that we did happened to coincide with would have to be described as the worst week of the entire campaign for Democrats,” pollster Steve Koczela told the radio station. “It was right after the first presidential debate, where President Obama gave what would have to be described as a pretty lackluster performance.”

Koczela added: “When you go from a four-point lead for one candidate to a five-point lead for another candidate, it is a meaningful change, definitely.”

The poll of 516 likely Massachusetts voters was conducted Oct. 21 to Oct. 22 by the MassINC Polling Group.