(CNN) - In their second debate in the Massachusetts Senate race, Republican Sen. Scott Brown on Monday sought to cement his image as an independent fighter, while Democratic opponent Elizabeth Warren attempted to tie the senator to the conservative base of the Republican Party.
"I vote about 50 percent with my party and about 50 percent with the Democratic Party," Brown said at the debate, held at the University of Massachusetts-Lowell. "That's a lot different than what Professor Warren would do."
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The Republican senator, who's running in a typically blue state, in particular sought to portray himself as an outsider to what he described as "dysfunctional" Washington. Brown won his Senate seat in a 2010 special election held to replace the late Ted Kennedy.
"I don't work for anybody. I don't work for President Obama or Mitt Romney or Mitch McConnell or Harry Reid," he said. "I work for the people of Massachusetts. That's what being an independent is all about."
While many Republicans spend their time blasting President Barack Obama on the campaign trail, the senator said he "was honored" to work with the president on certain pieces of legislation.
"Of course, I'm going to be proud to stand with the president," Brown said. "He is our president."
Pressed on whether Brown was trying to distance himself from Romney, who served as a Republican governor of Massachusetts, the senator said he lined up with the GOP nominee on economic issues–but said they didn't agree on everything.
"We're two different people," he said. Brown, however, attributed his lack of appearances with Romney to the presidential candidate's grueling schedule.
Sitting next to Brown at a table on stage, Warren took issue with the senator's self-portrayal as a bipartisan lawmaker.
Asked, however, whether she felt she could work with any current Republican members of the Senate, Warren named only retiring Sen. Dick Lugar of Indiana, who lost his seat in a heated primary battle earlier this year.
Pressed further, the Harvard law professor said it would "depend on the issue" and pointed to her experience "working across the aisle" when she served as Obama's adviser during the formation of the Consumer Financial Protection Bureau.
"At the end of the day, the reason I'm in this race is not about partisanship; it's about working families. I will work with anyone," she said.
Turning the tables back on Brown, Warren said the senator may talk a big game on his bipartisan credentials but argued the Republican makes a different case behind closed doors. Warren said Brown raises money by assuring donors he could help the GOP retake the Senate majority.
Furthermore, Warren said she "absolutely" believes Brown and the Republican Party aim to obstruct the president's agenda on economic issues, citing the senator's vote against jobs bills backed by Democrats.
"What Sen. Brown doesn't want to talk about is he has signed an extremist, right-wing pledge never to raise taxes on millionaires and billionaires," Warren added, referring to anti-tax heavyweight Grover Norquist's no-new-taxes pledge.
Bringing up an April vote in the Senate on the so-called Buffett Rule, a measure that would raise taxes on the very wealthy, Warren said, "Scott Brown, along with every other Republican, voted no."
She later added: "When it comes down to it in the hard votes, he stands with the millionaires. He stands with the billionaires….He's not there for people who are out of work."
The Republican senator countered, saying the Buffett Rule would only fund the government "for a day."
"We've been taxed enough, regulated enough, and the only person sitting at this table who's a fiscal conservative is me," he said, emphasizing his stance against raising tax rates.
The debate came one day after a new poll released Sunday indicated 43% of likely voters back Warren, while 38% support Brown. The five-point difference, however, falls within the survey's sampling error, meaning the two candidates are statistically tied.
The new survey marks the latest in a string of polls putting Warren ahead of Brown since the Democratic National Convention, where Warren delivered a high-profile speech. However, a University of Massachusetts/Boston Herald survey last week indicated Brown was up by four points.
A recent scandal surrounding Warren's claim to Native American roots also came up during Monday's debate, one week after both campaigns released dueling television commercials on the issue. Brown's campaign has been pounding Warren for citing Native American heritage in faculty directories at Harvard, something Warren says she did in order to meet people with similar backgrounds.
Warren on Monday reiterated that her mother told her she had such ancestry in her blood. The Democrat has long maintained that she never used her Native American claim to advance her career.
While the senator said it was not a disqualifying factor, he argued she has nonetheless been misleading to voters.
"No one's questioning about what our parents tell us as we grow up, but as you get older, she has an affirmative obligation to check," Brown said.
Hitting back, Warren faulted Brown for attacking her over the situation. "To try to turn this into something bigger is just wrong."
In a commercial last week, Warren responded directly to the jabs.
"As a kid, I never asked my mom for documentation when she talked about our Native American heritage," Warren said in the spot. "What kid would? But I knew my father's family didn't like that she was part Cherokee and part Delaware, so they had to elope."
"Let me be clear. I never asked for or never got any benefit because of my heritage," she continued. "The people who hired me have all said they didn't even know about it."