Discuss as:

In costliest-ever Senate race, Warren beats Brown for Massachusetts seat

Democrat Elizabeth Warren wins the Senate seat in Massachusetts, defeating GOP incumbent Scott Brown.

In perhaps the most-watched Senate race in the 2012 election, Harvard professor Elizabeth Warren is the projected winner of the Massachusetts seat once held by the late Sen. Edward Kennedy, NBC News reported.

Warren faced Republican Sen. Scott Brown, who swept to an upset victory in a January 2010 special election. Still, Brown was the underdog in the race against a Democrat known for her role in establishing the Consumer Financial Protection Bureau.

Brown — who referred to his opponent as "Professor Warren" at nearly every stop — suggested Warren had exploited her Native-American heritage to get jobs or get into schools. Warren said she heard about her Native-American roots from her mother and never use it to gain an advantage in her career.

“So much intensity in that race,” said NBC News' David Gregory, who moderated one of the debates between the candidates. “And don’t forget what Scott Brown represented. He was the vote against health care. He was the backlash that really represented and carried Republicans to the House and led the charge in the midterm election. He was also someone who tried as a mass moderate to work with the president and yet it wasn’t enough.”

The two candidates, The Associated Press reported, agreed to no outside money by super PACs and other independent groups then together spent $68 million on their campaigns, shattering all previous fundraising and spending records in Massachusetts.

NBC's Andrea Mitchell, Tom Brokaw and Brian Williams take a look at some key races at the state level across the U.S.

The Federal Election Commission reported Warren had raised $38.5 million in political donations as of mid-October, compared to Brown's $26.7 million. Brown's total doesn't include the $6 million left in his campaign account after the 2010 special election that propelled him into the Senate.

“Scott Brown would have had to win 20 percent of the Democratic vote to win against Elizabeth Warren,” said NBC News' Andrea Mitchell. “It was a very expensive, very hard fought race.”

Warren, 63, attempted to paint Brown, 53, as beholden to millionaires, billionaires and "big oil,” though the incumbent suggested he was an independent and moderate.

"I've kept my promise to be an independent voice. I put people ahead of politics and now I need your help to keep that independent tradition alive in Massachusetts," Brown said in his final ad, which features him embracing voters and driving his pickup truck. Still, he avoided any mention of Brown's party affiliation.

While Massachusetts is home to Republican challenger Mitt Romney — whose campaign Brown has endorsed  — the only image of a presidential candidate in the 60-second ad is Democrat Barack Obama, according to The Associated Press.

Scott Brown tells his supporters, "I don't want to see any sad faces out there. We ran a fantastic campaign." Watch his concession speech.

NBC News has projected the president as the winner in the state by a commanding margin over Republican challenger Mitt Romney. 

Warren cast herself as a fighter for the middle class.

“This victory belongs to you. You did this,” Warren said at her election party on Tuesday. “For every family that has been chipped and squeezed and hammered, we’re going to fight for a level playing field and we’re going to put people back to work."

Both campaigns boasted about their efforts to get out the vote. Warren's camp hoped to knock on a million doors and make 2 million phone calls in the campaign's final days. 

The Associated Press contributed to this report. 

More election coverage from NBCNews.com:

Follow NBC Politics on Twitter and Facebook