Republican US Senator Scott Brown portrayed himself as an independent voter and thinker in Washington, while his Democratic challenger, Elizabeth Warren, charged that he had voted “in lockstep’’ over and over with Republicans, as the two clashed in a debate at the University of Massachusetts Lowell tonight.

“I have a history of working across the aisle,’’ Brown said. “I take great pride in that independence.’’

“You need people down there who will actually work together,’’ he said during the fiery, hourlong debate.

But Warren said Brown’s attempt to portray himself as a bipartisan moderate was at odds with what he says when raising funds around the country, charging that he tells contributors that his victory would increase “the odds that Republicans will control the Senate’’ and make it possible to “block [President] Obama’s agenda,’’ if he were to win a second term.


“He stands with the millionaires. He’s stands with the billionaires. He’s not there for people who are out of work,’’ she said.

The two also wrangled again over Warren’s claims of Native American heritage and over the legal work that each has done.

Brown reiterated his call for Warren, a law professor at Harvard, to release her personnel records to prove that she had received no unfair advantage in getting the job from claiming to be Native American. And he said that she had “failed that test’’ of “integrity and character and trustworthiness.’’

Warren reiterated that she did not use her heritage to get “any advantage,’’ whether in applying to college, law school, or getting hired to any job.

She said she had learned of her heritage from her mother. And “I consider myself as having a Native American background. That’s what I said. That’s what I am.’’

“To try to turn it into something bigger is just wrong,’’ she said.

Brown criticized Warren’s representation of corporate clients, including a case where Warren represented Travelers Insurance, helping to secure a ruling that required Travelers to pay out $500 million to victims in exchange for immunity from future lawsuits. (In a later ruling, though, secured without Warren’s help, Travelers won an order to avoid paying out the $500 million.)


“It’s laughable to think that she was working for the victims to set up a trust,’’ Brown said.

But Warren said, “What I was out there doing was trying to help protect the asbestos victims. … The asbestos victims have stood up and said Senator Brown is wrong and he has crossed the line.’’

In one exchange that appeared destined to become a sound bite on the nightly news, Warren reeled off a litany of jobs bills that she said Brown had voted against with Republicans.

“First of all, she’s obviously misstating the facts,’’ began Brown. But then, when Warren attempted to interject, he said brusquely, “I’m not a student in your classroom, please let me respond.’’

The debate, held before a crowd of 5,700 at the university’s Tsongas Center, was co-sponsored by the Boston Herald and moderated by David Gregory, host of NBC-TV’s “Meet the Press.’’ The final two debates are Oct. 10 in Springfield and Oct. 30 in Boston.

The race is being closely watched nationally, as Warren and her fellow Democrats try to maintain control of the Senate, while Brown tries to help the GOP claim it, along with the US House and the White House.

The Globe reported Sunday that Warren appeared to be inching ahead in the race with a boost from Democrats energized by the presidential race, where Obama has appeared to make headway against Mitt Romney since the party’s convention.

When Gregory asked Brown if he would be a “reliable ally’’ for Romney, Brown, rather than giving a full-blown endorsement of his party’s presidential nominee, said, “I don’t work for anybody. I don’t work for President Obama or Mitt Romney or Mitch McConnell or Harry Reid. I work for the people of Massachusetts.’’


Asked if he was distancing himself from Romney, Brown said, “Listen, he’s out campaigning all over the country. I mean, I’m here in Massachusetts. I’m running in Massachusetts.’’

Brown was an obscure state senator from the town of Wrentham until he won a stunning victory against Attorney General Martha Coakley in the January 2010 special election to fill the seat left vacant by the death of long-time Democratic US Senator Edward M. Kennedy.

While he appeared to have been boosted by the Tea Party wave that would continue in the November 2010 elections, Brown has emphasized his independence as he seeks votes in the traditionally Democratic state.

Entering the race about a year ago, Warren was instantly seen as the Democratic frontrunner, a candidate with intellectual firepower and an eloquent populist-tinged message. She was known for her criticism of the financial industry, which she has accused of carrying out predatory practices. Her work in Washington included setting up a new consumer protection agency.