Senate Democrats have elected Senator Harry Reid of Nevada as their new leader, replacing Senator Tom Daschle of South Dakota, who was defeated in his reelection bid in this month's elections. Mr. Reid assumes his new post in January.

Mr. Reid will be the Democratic leader of a Senate with a larger Republican majority next year.

At a news conference Tuesday, Mr. Reid pledged that he would work with congressional Republicans and President Bush.

"We are going to work with the president," he said. "He said four years ago he wanted to be a uniter. He called me the day after the election and said he wanted to be a uniter. Didn't work too well the first four years; we hope it works the second four years, because we want to work together."

But the former amateur boxer said while he is willing to cooperate with Republicans, he would also fight for core Democratic principles.

"I would always rather dance than fight," he said. "But I know how to fight."

Mr. Reid is considered more centrist than many Democrats in the chamber. He voted for both the Gulf War resolution in 1991 and the Iraq war resolution in 2002. He often votes against legislation relating to abortion rights.

At the same time, he is viewed as a loyal Democrat, and he has won the respect of both moderates and liberals.

Mr. Reid expressed his disappointment over the Democrats' loss of four Senate seat in the November second election, and especially over his fellow Senate colleague John Kerry's unsuccessful bid for the White House.

He said he hoped Senator Kerry would play a prominent role in the Senate next year.

"We are looking for John Kerry to find what he wants to do," he said. "We are sorry he is not in the White House, but we are glad he is back on Capitol Hill."

The 64-year-old Mr. Reid was born in the small Nevada desert town of Searchlight to a father who worked as a miner and a mother who never finished high school.

Mr. Reid graduated from Utah State University and George Washington University Law School. During his law-school days he worked part-time as a Capitol police officer.

He was elected to the House of Representatives in 1982, where he served two terms, and then went on to serve 18 years in the Senate. He was reelected to his fourth term this month.