ATLANTA (AP) _ Former Ku Klux Klan leader David Duke announced today he is running for the Democratic presidential nomination, and predicted that his campaign could ''change America now and in the future.''

Duke, who now heads the National Association for the Advancement of White People, told a news conference on the steps of the Georgia Capitol that the race will narrow to a confrontation between him and the Rev. Jesse Jackson.

''I have a strong constituency of white working people. Jesse Jackson has got a strong constituency obviously among the black bloc vote. I think the dynamics of a political confrontation between myself and Jesse Jackson will mean that we will receive a great deal of votes in the Democratic Party,'' he said.

Duke said the American middle class would ''speak out in this election. ... The ramifications of this campaign will change America now and in the future.''

About 30 supporters joined Duke at the Capitol, where the event was moved after at least two hotels proved unwilling to provide facilities.

Although Duke has called for an end to affirmative action for minorities and claims school desegregation ruined the nation's schools, he insisted he is not a white supremacist.

Instead, he said, he is a white civil rights activist.