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.

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.

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:

• Obama wins re-election; Ohio, Iowa, Wisconsin prove pivotal
• Democrats gain in Senate with wins in four states
• Maine's Harley-riding King vowed to 'shake up' D.C.
• In costliest-ever Senate race, Warren beats Brown for Mass. seat
• Republicans to maintain control of House, NBC News projects
• In 11 governor races, it's about jobs and taxes
• Majority of voters see American on wrong track

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Updated at 2:00 p.m. ET, Nov. 7: Democrats added another seat in the Senate on Wednesday, according to NBC News projections, strengthening their control of the Senate. 

Democrat Heidi Heitkamp was declared the winner of the North Dakota senate race Wednesday, defeating Republican Rep. Rick Berg. See results

Earlier, Democrat Jon Tester was declared the winner over Republican Rep. Denny Rehberg in Montana, a contest which saw an estimated $40 million spent in a state with fewer than 1 million residents. See results

Those victories, which gave Democrats control of 53 seats in the Senate -- along with one independent, Bernie Sanders of Vermont, who caucuses with them -- kept the party's edge in the upper chamber of Congress.

Independent Angus King of Maine won an open Senate seat that had been held by Republican Olympia Snowe, NBC News projected. King could vote with the Democrats, though he hasn't yet said which party, if any, he will side with. 

Maine independent promised to shake up Washington

With the House remaining in Republican hands, the makeup of the government will remain static: President Barack Obama was re-elected, but he will have to contend with a divided Congress for four more years.

"Things like this are what happens when your No. 1 goal is to defeat the president and not work to get legislation passed," Senate Democratic leader Harry Reid of Nevada said in a statement. 

In a statement of his own, Republican leader Mitch McConnell of Kentucky challenged Obama to "propose solutions that actually have a chance of passing the Republican-controlled House of Representatives and a closely divided Senate."

"To the extent he wants to move to the political center, which is where the work gets done in a divided government, we'll be there to meet him halfway," McConnell said.

View complete Senate election results

The Democrats clung to control on the back of a series victories in states that had been statistical ties in pre-election polls:

• Harvard University law professor Elizabeth Warren ousted Republican Sen. Scott Brown in Massachusetts, NBC News projected. Massachusetts results
• Republican state legislator Deb Fischer defeated former Sen. Bob Kerrey for the open seat of retiring Democratic Sen. Ben Nelson, NBC News projected. Nebraska results
• Democratic former Virginia Gov. Tim Kaine beat former Republican Gov. George Allen, NBC News projected, keeping the seat held by the retiring Sen. Jim Webb in Democratic hands. See results
• Democratic Rep. Joe Donnelly of Indiana defeated Republican state Treasurer Richard Mourdock to claim the open seat held by Republican Dick Lugar, NBC News projected. Mourdock had been favored until he drew national opposition for having said in a debate last month that he believed that pregnancies resulting from rape were a "gift from God" and shouldn't be terminated. See results
• Democratic Sen. Claire McCaskill held on to her seat in Missouri after Republican Rep. Todd Akin made similar comments in a TV interview in August, suggesting that women's bodies could "shut down" a pregnancy that was the result of a "legitimate rape." See results

As expected, Rep. Martin Heinrich, D-N.M., defeated Republican former Rep. Heather Wilson to win the open seat of retiring Republican Jeff Bingaman, and Rep. Tammy Baldwin, D-Wis., beat Republican former Gov. Tommy Thompson to become the nation's first openly gay senator, NBC News projected. New Mexico results 

Thompson, who served as secretary of Health and Human Services in the administration of former President Geoorge W. Bush, announced his retirement from politics in his concession speech. Wisconsin results

Wisconsin's Baldwin becomes first openly gay senator

Democrats entered Tuesday with control 53 seats in the current Senate (that number included Sanders and Joe Lieberman of Connecticut, an independent who also generally voted with them); Republicans held 47.

Ten senators weren't seeking re-election this cycle — the most since 1996. In addition, Lugar lost to Mourdock in the Indiana Republican primary, meaning at least 11 new faces will join the Senate on Jan. 2.

Exit polls: Majority of voters see America on wrong track

Warren's victory was particularly sweet for Democrats, for whom she was a hero as the architect of Obama's U.S. Consumer Financial Protection Bureau.

"You took on the powerful Wall Street banks and special interests, and you let them know you want a senator who will be out there fighting for the middle class all of the time," she told cheering supporters in Boston.

The races in Missouri and Indiana were also closely watched because of the controversies generated by Akin's and Mourdock's comments on abortion.

McCaskill reveled in her victory, giving supporters a beaming I-told-you-so speech in St. Louis.

"They all said it's over — it's done, it's too red, it's just too red," she said. "There is no way that Claire McCaskill can survive. Well, you know what happened? You proved them wrong."

Akin told supporters in Missouri that he had called to congratulate McCaskill, but he sounded a defiant note:

"I also think, in the circumstances that we've all been through, that it is particularly appropriate to thank God, who makes no mistakes and is wiser than we are," Akin said.

"... Washington, D.C.'s first questions shouldn't be what's politically expedient, but what's right," he said. "Washington doesn't need more money. It needs more courage."

Donnelly, meanwhile, stressed bipartisanship, telling supporters in Indianapolis that he hoped to follow in the moderate shoes of two predecessors, Lugar and Democrat Evan Bayh.

"I say to all of my fellow Hoosiers out there: This isn't about politics. This isn't about one party or the other," Donnelly said.

More election coverage from NBCNews.com:

• Obama wins re-election; Ohio, Iowa, Wisconsin prove pivotal
• Democrats gain in Senate with wins in four states
• Rape remarks sink two Republican Senate hopefuls
• In costliest-ever Senate race, Warren beats Brown for Mass. seat
• Maine's Harley-riding King vowed to 'shake up' D.C.
• Republicans to maintain control of House, NBC News projects
• Colorado, Washington approve recreational marijuana use
• In 11 governor races, it's about jobs and taxes
• Majority of voters see American on wrong track

Follow NBC Politics on Twitter and Facebook

Republican U.S. Senator Scott Brown and his Democratic opponent Elizabeth Warren engaged in a fiery debate Monday night as Brown insisted that he has a history of working across the aisle while Warren said his attempt to appear moderate was at odds with what he says while fundraising.   

“He stands with the millionaires. He stands with the billionaires. He’s not there for people who are out of work,” said Warren, a Harvard Law School professor, according to the Boston Globe.

Brown, meanwhile, pushed Warren to name a single Republican she could work with in the Senate.

She finally named Indiana Senator Richard Lugar, who lost his primary fight in the spring to a more conservative Republican.

The candidates also debated Warren’s Native American heritage. Brown asked her to release her personnel records, the Globe reported; Warren rebutted that she had learned about her heritage from her mother and that she hadn’t received advantages. 

“To try to turn it into something bigger is just wrong,” she said, according to the Globe. Brown, 53, has suggested in the past that Warren has exploited her background to get jobs or get into schools.

The televised debate was held at the University of Massachusetts-Lowell, co-sponsored by the Boston Herald – which described the debate as a slugfest – and moderated by NBC’s David Gregory before a raucous crowd of more than 5,000. Scott and Warren will face off again on Oct. 10 in Springfield and Oct. 30 in Boston.

When Warren listed job bills, saying that Brown had voted against them in step with the GOP, Brown countered that she had misstated the facts. When Warren tried to interrupt him, he testily replied, “I’m not a student in your classroom, please let me respond.”

(Brown has referred to her as “Professor Warren” in debates, which Warren says she doesn’t mind, according to The Associated Press.)

The candidates disagreed about Afghanistan, although both strayed from party lines. Warren said she would withdraw U.S. troops before the 2014 deadline set by the president; Brown said he wouldn’t want to cross the president, the AP reported.

They even debated whether the Red Sox manager should be given another year, the Boston Herald reported. Warren said Bobby Valentine should be given another year; Brown recalled that Warren had previously predicted that Red Sox would win 90 games.

Recent polls show Warren, 63, a Harvard Law School professor and former official in President Barack Obama's administration, maintains a slim lead over Brown, who swept into the Senate in a special election in 2010 after the death of revered Democratic Senator Edward Kennedy.

Christopher Evans / AP

Republican Sen. Scott Brown, left, answers a question during a debate against Democratic challenger Elizabeth Warren, center, sponsored by the Boston Herald at the University of Massachusetts in Lowell, Mass., Monday, Oct. 1, 2012.

Democrats have a 51-47 advantage over Republicans in the 100-seat U.S. Senate, with two independents. However, they are defending more than 20 seats against Republican challengers, while Republicans are defending only half that many.

Reuters contributed to this report.