"I think that the campaign that we are beginning to officially to embark upon will change American politics. ... The Democratic party cannot win unless it expands its base," Sharpton said at a news conference immediately after filing the papers at the Federal Election Commission offices.
The 48-year-old civil rights leader said he was the only candidate who is "anti-war, anti-death penalty, anti-tax cut across the board." Sharpton said he would reach out to disaffected voters, including Latinos, blacks, gays and lesbians, and young people.
Sharpton, who has unsuccessfully run for mayor and the U.S. Senate, has been outspoken on many local and national issues, most notably on police brutality.
He also served 90 days in a federal jail for protesting the U.S. military bombing on the tiny Puerto Rican island of Vieques.
Sharpton joins a crowded field of Democratic contenders, including John Kerry of Massachusetts, John Edwards of North Carolina, and Joseph Lieberman of Connecticut. Rep. Dick Gephardt, of Missouri, also is likely to run. Former Vermont Gov. Howard Dean was the first Democrat to declare his candidacy.