Republican incumbent Scott Brown (48 percent) clings to a one-point lead over Democratic challenger Elizabeth Warren (47 percent) in the Massachusetts race for the U.S. Senate, according to a Suffolk University/7NEWS (WHDH-Boston) poll of likely general-election voters in Massachusetts.

The poll result is well within the margin of error. Five percent of voters were undecided in a race that has drawn interest from across the country, even though the primaries are months away. The race has closed since a February Suffolk University/7NEWS poll showed Brown leading Warren 49 percent to 40 percent, with 11 percent either undecided or choosing someone else.

“In both the February and May polls, Brown has fallen short of the coveted 50 percent mark for an incumbent, while Elizabeth Warren has converted some undecided voters since February,” said David Paleologos, director of the Suffolk University Political Research Center in Boston. “This leaves both campaigns no choice but to spend tens of millions of dollars in an all-out war to woo the five percent of voters who will decide this election.”

Warren’s heritage

Seventy-two percent of likely voters were aware of the recent controversy concerning Elizabeth Warren’s heritage. Of those, 49 percent said Warren was telling the truth about being part Native American; 28 percent said she was not telling the truth; and 23 percent weren’t sure. Meanwhile, 41 percent said they believed that Elizabeth Warren benefited by listing herself as a minority, while 45 percent said she did not benefit. Sixty-nine percent of likely voters said that Warren’s Native American heritage listing is not a significant story, while 27 percent said that it is.

Brown and Wall Street

On the flip side, Warren’s claim that Scott Brown is a Wall Street favorite did not have traction with voters. When likely voters were asked if a vote for Scott Brown is a vote for Wall Street, 55 percent disagreed and 33 percent agreed. And voters were split on whether he should return the $50,000 dollars his campaign received from JP Morgan Chase employees, with 43 percent saying he should not return the money and 42 percent saying he should.

Favorability shifts

Brown’s popularity (58 percent favorable) moved up six points from February (52 percent favorable), while his unfavorable rating remained the same at 28 percent. Warren gained 8 points on her favorable rating (43 percent) since February, when it was 35 percent, but she also tacked 5 points onto her unfavorable rating, which is now 33 percent unfavorable, as opposed to 28 percent in February.

Warren’s recent TV advertising buy included a testimonial from President Barack Obama, who recorded a 62 percent favorable and 32 percent unfavorable rating in the poll.

“To win a second term, Brown will have to make the case for why he deserves to be reelected rather than suggesting that Warren is not fit to be the U.S. senator,” said Paleologos.

“And a winning strategy for Warren would be twofold,” he said. “She should expand the middle-class theme across the Massachusetts political landscape, and she should court undecided voters, who in two polls have shown reluctance to pull the trigger for Scott Brown. Continuing to align herself with President Obama will help her cause with independents.”

The poll showed that general election voters of all parties like having one Democratic and one Republican Senator in Washington, a point of view that could tip a close race to Brown. Fifty-six percent said there is a benefit to having a member of each party representing Massachusetts in Washington, while 38 percent said there is no benefit.

In evaluating the two candidates, 47 percent of likely voters said that Brown will be an independent U.S. senator, while 42 percent said the same of Warren. More voters said that Brown has run the better campaign (42 percent) compared to Warren (23 percent). Warren was seen as representing the interests of middle-class families by 49 percent of voters and Brown by 36 percent.

Presidential race

The presidential race in Massachusetts will be no contest, whether measured by voter reality or by perception. Obama (59 percent) led former Gov. Mitt Romney (34 percent) by 25 points among likely voters. Obama led by more than 35 points when these same voters were asked who they believed would be elected as the next president regardless of their personal preference (Obama, 58 percent, Romney, 23 percent).

With 80 percent of voters aware of the 1965 incident when Romney was accused of forcibly cutting the hair of a prep school classmate, 46 percent said that Romney was a bully, while 40 percent said he was not.

Suffolk University’s was the first poll using live interviewers to show Republican Scott Brown leading Democrat Martha Coakley -- by 4 points -- on Jan. 14, 2010. Five days later, Brown won the Senate seat by 5 points.

Methodology

The statewide survey of 600 likely Massachusetts general election voters was conducted May 20-22, 2012, using live telephone interviews of landline and cell phone users. The margin of error is +/-4 percent at a 95 percent level of confidence. Marginals and cross-tabulation data will be posted at 11 p.m. Wednesday, May 23, on the Suffolk University Political Research Center website. For more information, contact David Paleologos at 781-290-9310, or follow on Twitter