"Gov. Dean has the energy to inspire the American people, to break the cocoon of fear that envelopes us and empowers President Bush and his entourage from the extreme right-wing," she said at a joint appearance with the former Vermont governor.
Dean said Wednesday that he welcomed Braun's endorsement.
"She's a principled person. We just hit it off. I like her a lot," Dean told reporters at a hotel in Fort Dodge, Iowa, where he was spending the night after starting a statewide bus tour.
"It's going to be a big help to us," he said.
But Braun's endorsement isn't likely to boost Dean's chances of winning Iowa, since he appears to be losing ground.
In the latest Reuters/MSNBC/Zogby poll, Massachusetts Sen. John Kerry had edged Dean and Missouri Rep. Dick Gephardt for a slight lead in caucus polling.
After trailing Dean by as much as 11 points earlier in the week, Kerry now has 22 percent of the vote -- a single point lead over the previous front-runner, who is tied with Gephardt. The poll with the 4.5-point margin of error gives North Carolina Sen. John Edwards 17 percent, making it a 4-man race.
All other possible contenders for the Democratic presidential nomination have 3 points or less in Iowa.
With the clock winding down to the nation’s first presidential caucus in Iowa next week, Braun’s withdrawal winnows the crowded field of Democratic contenders to eight. Her decision to throw her support behind Dean may be a bright spot in what has been a week of fever-pitch attacks against, and missteps by, the front-runner.
During Sunday’s debate in Des Moines, Braun stepped in several times to defend Dean against attacks on race issues by the only other black candidate in the race, Al Sharpton (search).
Braun and Dean had met since then to discuss her core issues and get his views on them, especially affirmative action.
Braun is giving Dean her endorsement even as he has faced questions about his record on race issues, including his lack of minority Cabinet members during his five terms as Vermont governor.
Braun’s only significant endorsements had come from the National Organization for Women and the National Women's Political Caucus. As the only black woman in the race, Dean and Braun aides argued that her support would help him with blacks and women.
As a practical matter, Braun’s endorsement does not have much to offer Dean. But at a time when Dean needs good news because the latest tracking polls show Gephardt, Kerry and Edwards gaining on him, the Dean camp welcomed the endorsement eagerly.
Braun had almost no campaign organization in any state, including South Carolina, where minorities are expected to make up half of the electorate on the Feb. 3 primary. She never broke out of single digits in national surveys, didn't qualify for several state ballots and ran up thousand of dollars in campaign debt. Even her own campaign manager, Patricia Ireland, had said publicly there was no way Braun could win the nomination.
Braun is the second Democratic presidential candidate to pull out of the race before the start of voting on Jan. 19 with the Iowa caucuses. Sen. Bob Graham of Florida withdrew from the race on Oct. 6.
Braun became the first African-American woman elected to the U.S. Senate in 1992. Representing Illinois, she was the first permanent woman member of the Finance Committee, a member of the Banking, Housing and Urban Affairs Committee and a member of the Special Committee on Aging.
But she ended her Senate term haunted by scandals, including a Federal Elections Commission probe into whether she had pocketed nearly $250,000 in campaign funds. She was also roundly criticized by fellow black lawmakers and human rights groups for meeting with the late dictator Sani Abacha during a trip to Nigeria in 1996.
Braun lost her bid for re-election to Republican Peter Fitzgerald in 1998, after which she was named ambassador to New Zealand by President Clinton.
Braun did not have a major impact in the race for the Democratic nomination, but some political observers have viewed her presidential candidacy as an effort to rebuild her reputation.
Fox News' Carl Cameron, Jane Roh and The Associated Press contributed to this report.