By Jim Finkle
BOSTON (Reuters) - Democrat Elizabeth Warren defeated incumbent Massachusetts Senator Scott Brown on Tuesday in one of this year's most expensive and closely watched congressional races.
The victory of the 63-year-old Harvard University professor and architect of a new U.S. agency to police consumer finance gives Democrats back a seat held for almost five decades by liberal stalwart Edward M. Kennedy and helped prevent Republicans taking a majority in the Senate.
Brown took his current office in a 2010 special election to fill the seat vacated by the death of Kennedy. The former Republican State senator, known for his common man persona and pickup truck portrayed himself as a moderate to voters in the liberal state, pointing to a record as one of the most bipartisan members of the U.S. Senate.
Warren countered that strategy by telling voters that his re-election could help the Republicans gain a majority in the Senate.
"We're going to hold the big guys accountable," Warren told a boisterous crowd of about 1,000 supporters ranging from college students in jeans to professionals in business suits. "I won't just be a senator, I will be your champion."
A consumer advocate, Warren conceived the idea of the U.S. Consumer Protection Bureau, formed to monitor the market for mortgages, credit cards and other consumer financial products.
Gathered at a swanky downtown Boston hotel, Massachusetts Democrats celebrated the win in one of the most-closely-watched races in the liberal state.
"This is a very special senate seat. It's the people's seat," said former Massachusetts Governor Michael Dukakis. "It was occupied by a rare human being and a great American. We need somebody in that seat who reflects Ted Kennedy's values and his commitment to working people's families."
Brown told supporters he had already congratulated his successor.
"You've got no business in politics unless you respect the judgment of people," he told a gathering of hundreds. "I respect the decision of voters and I've already offered by respects to Senator Warren."
Democrats retained control of the U.S. Senate on Tuesday night.
(Reporting By Jim Finkle; Editing by Scott Malone and Alden Bentley)