Stark contrast, close call in Massachusetts Senate race (CBS News) In this election, Republicans will be trying to win back control of the U.S. Senate. And one of the key races is in Massachusetts where polls show a tight battle between the Republican incumbent, Scott Brown, and his Democratic challenger, Elizabeth Warren. Sen. Scott Brown and his opponent Elizabeth Warren had been campaigning themselves hoarse. "I'm afraid my exuberance is now showing up in my voice," said Warren. For Warren, a Democrat and Harvard University law professor, it's a sprint to introduce herself to 4 million Massachusetts voters. Warren defends slow response to heritage questions Mass. Senate race tight after Warren controversy Warren blasts Brown for "nasty insinuations" about history "I've been watching for 20 years as America's middle class just gets hammered," Warren told CBS News. Brown is a Republican who won a surprise victory in this blue state to fill the seat of one of the Senate's legendary liberals, Ted Kennedy. Now Brown is out to prove it wasn't a fluke. "I've been able to go in there as that independent person voting on every issue," Brown said. I don't work for Harry Reid or Mitch McConnell -- I work for the people of Massachusetts. They both have a record of breaking through Washington gridlock. Warren took on government and Wall Street when she was asked by Sen. Majority Leader Harry Reid to monitor the financial bailout. Then she led the charge to create a new consumer protection agency. Brown successfully sponsored laws to make it easier for entrepreneurs to raise capital, and to prevent members of Congress from using inside information to profit in the stock market. Asked why Massachusetts voters should elect for someone other than Scott Brown, Warren responded: "Well, I think this one is really about whose side do you stand on. Scott Brown has been delivering for Wall Street. Brown's response: "Well, with all due respect, she's had some credibility issues lately." He's talking about the controversy over Warren's decision, while at Harvard and the University of Pennsylvania, to list herself in professional directories as "Native American." There's no evidence of her having any Native American. She's not 1/32nd, there's none," Brown said. Warren said she always told by her parents that she has Cherokee and Delaware Indian blood. "I know my family's heritage," she said. It's also been clear from the very beginning that I never got any special breaks from it. Recent polls show most voters in Massachusetts don't think that Warren's heritage is a big deal. These two candidates are in a statistical dead heat.