Sen. Scott Brown (R) led Democrat Elizabeth Warren by 1 point among likely voters in a new poll, casting drops of doubt on the conventional wisdom that Warren had pulled into a comfortable and nearly insurmountable lead in the weeks before Election Day.

While the vast majority of recent reputable polling has shown Warren comfortably ahead of the incumbent, a new UMass Lowell/Boston Herald poll found Brown leading Warren 49 percent to 48 percent among Massachusetts registered voters likely to vote. One percent didn’t know and one percent said they would vote for someone else.

Among all registered voters, Warren led Brown by 2 points.

With the abundance of polling in the race, the UMass Lowell poll appears to be an outlier. And even if it’s spot on, Democrats believe their robust, grass-roots turnout operation — which they’ve been honing since Brown’s surprise special election victory in January 2010 — is likely to help Warren do a bit better than polls of likely voters indicate.

Among registered voters, 54 percent had a favorable view of Brown, while 39 percent had an unfavorable view of the Senator. Fifty percent had a favorable view of Warren, while 42 percent had an unfavorable view of her. Both candidates have hammered the other side with millions of dollars of negative ads.

The UMass Lowell poll surveyed 956 registered Bay State voters on cellphones and land lines by live telephone interviews chosen by random digit dialing from Oct. 31 through Nov. 3. Based on the survey’s screen, 800 of those respondents were considered likely to vote. The margin of error among registered votes was 3.7 points. The margin of error among likely voters was 4.1 points.