Cheers filled the hotel ballroom here where Ms. Warren was holding her victory party as word of her win came out.
Nearly three-fourths of voters in Massachusetts went to the polls on Tuesday, a turnout higher than the 3.1 million who voted in the 2008 presidential race.
The Senate seat had slipped — temporarily, as it turned out — into Republican hands when Scott P. Brown, a state legislator, won it in a special election in 2010 after Mr. Kennedy’s death. Taking it back was a Democratic priority.
With many voters waiting an hour or more to cast their ballot, Ms. Warren, who had no appointments on her schedule Tuesday, visited at least eight polling places to encourage them to the endure the wait. Mr. Brown, the Republican incumbent, visited sites as well.
With the win, Ms. Warren, 63, a Harvard professor who set up the Consumer Financial Protection Bureau in the Obama administration, becomes the first woman to represent Massachusetts in the Senate. She had made a forceful appeal to women, who overwhelmingly supported her bid, while men favored Mr. Brown.
She cast herself as a fighter for the middle class and a champion of women’s causes, particularly equal pay for equal work, health insurance coverage for birth control and abortion rights.
It was a message that resonated with Elizabeth Lear, 46, a book reviewer in Waltham, who said she voted for Ms. Warren because “she cares about the financial concerns of everybody and most importantly about women’s reproductive rights, the freedom to choose.”
And, Ms. Lear added, “I feel she’s pretty scrappy and I really like that about her.”
Mr. Brown cast Ms. Warren as a partisan and inflexible ideologue who would march in lock step with the Democratic Party.
Their race cost more than $68 million, making it one of the most expensive Senate races in the country. With the help of progressive groups that bolstered her candidacy early, she raised a stunning $39 million, which put her among the top five most successful Senate fund-raisers of all time. The money was all the more remarkable considering that Ms. Warren was a first-time — and untested — candidate.
“We raised money from more donors than any Senate campaign in the history of the United States,” Ms. Warren said in a statement about an hour after the polls closed Tuesday and before she made her victory speech at the Fairmont Copley Plaza hotel here. She added: “We knocked on more doors and made more phone calls than any candidate in the history of the Commonwealth of Massachusetts.”
Both candidates had been delivering their messages to residents for months. And on Tuesday, voters in Waltham — a bellwether district that Mr. Brown won in 2010 by a percentage point — made it clear that those messages were received.
“Bipartisanship,” said Jennifer Heizer, 30, who works in health care information technology, as she explained why she voted for Mr. Brown.
“I think he keeps a little more in touch with the people,” Ms. Heizer said. “He seems a little more down to earth, someone who will be sincere in working across party lines to accomplish his goals.”
Vic Pompa, 65, who is retired from the investment compliance industry, said he liked Mr. Brown because he was a “pro-capitalist.” Mr. Pompa described Ms. Warren as a “limousine liberal who is running a generic Democratic campaign from the 1930s or the 1960s, where she talks about big oil and millionaires and billionaires and other nonsense.”
Wesley Burge, 71, who is retired from the military, liked Mr. Brown because he was a veteran. Of Ms. Warren, he said: “If she was dressing for a job interview, I don’t think she’d get the job. She’s wearing either a house coat or a smock, whatever you call it, and slacks. I’ve never seen her in a dress, as a lady. Her appearance doesn’t set well.”
But supporters of Ms. Warren were just as vocal.
Ronald Nigro, 44, a wine salesman, said he had been torn. He said he liked that Ms. Warren is a consumer advocate who “stands up for the people,” and he said Mr. Brown is “a good man.” He voted for Ms. Warren.
“If the Democrats already had a 60-40 majority in the Senate, I’d consider voting for Scott Brown,” Mr. Nigro said. “But unfortunately the situation is what it is and President Obama needs another Democrat in the Senate.”