The state's largely Democratic electorate, coupled with Warren's pulling women voters to her side, proved too much for Senator Brown to overcome.

Brown was popular and benefited in this "blue" state by avoiding lock-step votes with Senate Republicans. But unlike 2010, when he won his seat in a special election, this was a presidential year that brought out a broader array of the state's electorate. The race this year also brought in massive amounts of campaign contributions on both sides, as Republicans sought to defend a seat and Democrats sought to reclaim it.

Ms. Warren is a stalwart liberal who became known nationally as a crusader against the power of Wall Street banks and for her focus on the economic struggles of working-class families.

"It was exactly 50 years ago tonight that Ted Kennedy was first elected to the United States Senate," Warren told cheering supporters Tuesday night. "We miss his passion, his commitment, his energy, and his fight for working families."

Warren said that Mr. Kennedy's pledge back then – to devote all his strength and will to serving Bay State residents – is now hers as well.

Both candidates maintained a positive impression with voters during the campaign. Yet the campaign was also rife with negative ads.

Warren's ads appealed especially to women, and they did so successfully.

"Don't let Scott Brown put women's health at risk," one Warren flier warned as Election Day neared. The mailing said Brown had, among other things, "stood with Republican extremists against Planned Parenthood, voting to limit access to preventive care."

Warren also bored in on the national implications of the race, arguing that a vote for Brown would also be a vote for expanding the clout of Republicans in the Senate – many of whom are more conservative than Brown. She reminded voters that the next senator from Massachusetts could have a role to play in anointing Supreme Court nominees, and she sought to raise doubts about Brown's commitment to abortion rights.

Warren fended off attacks by Brown, including his questioning of her integrity during her academic career. She had listed herself as a minority in a directory of law-school professors for many years, then dropped the listing after gaining a position at Harvard Law School. Warren rejected the implication that she had used the listing to advance her career, and most voters didn't hold the issue against her.

After the hard-fought race, Brown was gracious in conceding defeat. "She won it fair and square folks," he told his campaign staff. "May she bring that Senate office great credit."

Warren, too, sounded a magnanimous note. She said although Brown's supporters didn't vote for her, she embraced his message of being ready to work across party lines. "I promise I'm going to work to earn your support," Warren said.