BOSTON -- Republican incumbent U.S. Sen. Scott Brown and Democratic rival Elizabeth Warren sparred on tax policy, Iran's nuclear ambitions and Warren's claims of Native American heritage during their first debate in Massachusetts' closely watched Senate race.
Brown began the debate by saying Warren "checked the box claiming she is Native American, and clearly she is not."
Brown called on Warren, a professor at Harvard Law School, to release records related to her hiring at the school to show whether she got an unfair advantage.
"I think character is important," he said.
Warren said that her parents told her growing up that her mother was part Cherokee and part Delaware Indian and that as a child she never questioned that story.
Warren also said those who hired her during her law school career had said they were either unaware of her background or that it played no role in their decision to hire her.
"This is about family. I can't and I won't change who I am," she said.
Warren shot back at Brown, saying voting for him could turn control of the Senate over to Re publican leaders.
"I am working to keep President (Barack) Obama as our commander-in-chief," she said, "not Mitt Romney."
Warren pointed to a series of Brown votes in the Senate that she said show he sided with big oil companies and held tax cuts for the middle class hostage to give tax cuts to millionaires.
"Sen. Brown is out there protecting every loophole," she said.
Brown responded by saying of the two candidates in the race, only one supports higher taxes, and that's Warren. He also said putting more financial pressure on oil companies could raise prices at the pump.
"I am on the taxpayer's side," he said, noting that it's now costing him $70 to fill up his pick-up truck.
There were several testy exchanges during the hourlong debate on WBZ-TV.
Warren tried to portray Brown as unreliable on women's issues. Warren said she would not vote to support a U.S. Supreme Court nominee who opposes legal abortion. She criticized Brown for opposing the nomination of Elena Kagan to the court.
Brown described himself as "pro-choice" and said he opposed Kagan because she didn't have enough courtroom experience for the high court. "Sorry I didn't vote for your boss," Brown said, referring to Kagan's tenure as dean of Harvard Law School.
Warren also pointed to a Brown vote in favor of a proposed amendment that would allow employers to deny insurance coverage for birth control. Brown said he supports women's access to birth control but was trying to protect the concerns of Roman Catholics.
Asked about the possibility that Iran could acquire a nuclear weapon, Brown criticized Warren for not adopting a tough enough response. "We cannot have a nuanced approach that Professor Warren wants," he said.
Warren said she also supports Israel and is opposed to allowing Iran to gain nuclear arms. She also praised Secretary of State Hillary Rodham Clinton and Obama, saying he's "done a first-rate job. He's taking nothing off the table."
The two sparred on energy and higher education. Brown said he's taking an "all-of-the-above" approach to energy policy from natural gas to renewable energy.
He also criticized Warren's $300,000 salary at Harvard, saying administrative costs are driving up tuition. He said he filed a bill for more fiscal transparency at colleges and universities.
Warren said the problem is that the United States isn't investing enough in education. She said Brown is more interested in protecting tax breaks for the wealthy than in making it easier for young people to get college degrees.
Polls show a close contest. The race is already the most expensive campaign in Massachusetts political history.