The results show Warren recovering from the down-ballot effects of President Barack Obama's poor performance in the first presidential debate, as well as benefiting from her own debate performance, MassINC pollster Steve Koczela said. MassINC's last poll, taken from Oct. 5-7, showed Brown ahead by 3 points -- the only survey since September to show him with a lead.
"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," Koczela told WBUR. “It was right after the first presidential debate, where President Obama gave what would have to be described as a pretty lackluster performance."
Other polls at the time did not show a similar dip. Of the 10 surveys of the Massachusetts Senate race released in October, all but the previous MassINC/WBUR poll showed Warren as ahead, with the margin of her lead ranging from 2 to 9 points.
HuffPost Pollster, which tracks all publicly available polls, has Warren's numbers steadily improving through the summer, currently putting her ahead by a little over 3 points.
The new MassINC/WBUR poll surveyed 516 likely voters by phone between Oct. 21 and 22, with a 4.4 percent margin of error.