"This is going to be a moment that you'll never be able to paint people as haters, racists, none of it," he says of the event featuring Sarah Palin and other conservative political and cultural figures. "This is a moment, quite honestly, that I think we reclaim the civil rights movement."
Some civil rights veterans are skeptical.
"When we heard about Glenn Beck, it was puzzling," the Rev. Al Sharpton said. "Because if you read Dr. King's speech, it just doesn't gel with what Mr. Beck or Mrs. Palin are representing."
Beck, a popular figure among tea party activists and a polarizing Fox News Channel personality, is headlining the event, and Palin, the 2008 Republican vice presidential nominee and a potential 2012 president candidate, will be a prominent speaker. But Beck told his television audience again on Thursday that it's not about politics.
The event's website says the rally is to pay tribute to America's military personnel and others "who embody our nation's founding principles of integrity, truth and honor." It also is to promote the Special Operations Warrior Foundation, which provides scholarships and services to family members of military members.The website urges citizens to attend and "help us restore the values that founded this great nation."
The rally, on the 47th anniversary of King's plea for racial equality is drawing a strong reaction - and several counter-rallies - as the nation looks toward November's elections.
Beck is known for his strong opinions, including his statement that President Barack Obama is a racist; he later told CBS' Katie Couric that he was "sorry the way it was phrased."
But organizers of Saturday's rally are telling attendees not to bring signs, "as they may deter from the peaceful message we are bringing to Washington."
Signs at some tea party events have included pictures of Obama embellished with a Hitler-style mustache, racial epithets and threats to Democratic officials. Such posters have given tea party critics grounds to claim the loose organization of activists is motivated by racism against the nation's first black president.
"Dr. King never had to ask anyone to leave their signs and guns at home," said Benjamin Todd Jealous, president of the NAACP. "To say to your followers, don't bring your signs - it's like saying don't open your mouth."
"The 8-28 rally is supposedly is about 'reclaiming the civil rights movement,' but it is being led by someone whose idea of a racist is the president of the United States," said Jess Levin, a spokesman for the liberal Media Matters for America. "This rally is about one thing and one thing only. And that's promoting Beck's political agenda."
Elsewhere in Washington, civil rights activists planned to mark Saturday's anniversary of the landmark 1963 speech with rallies and demonstrations, some ending on the National Mall. One group planned a four-story sculpture in honor of King near the Washington Monument. Others planned to meet at a Washington school.
Sharpton's National Action Network planned a "Reclaim the Dream" rally featuring Education Secretary Arne Duncan, National Urban League president Marc Morial and Martin Luther King III.
In an opinion piece for The Washington Post, King said of Beck's event that it's "commendable that this rally will honor the brave men and women of our armed forces who serve our country with phenomenal dedication." But he also said it was clear the organizers were invoking his father's work.
"My father championed free speech. He would be the first to say that those participating in Beck's rally have the right to express their views," King wrote Wednesday. "But his dream rejected hateful rhetoric and all forms of bigotry or discrimination, whether directed at race, faith, nationality, sexual orientation or political beliefs."
In the 47 years since King's speech, it has become a staple of civil rights history.
"I have a dream that my four little children will one day live in a nation where they will not be judged by the color of their skin but by the content of their character," he said on Aug. 28, 1963.
Beck has sought to play down any comparisons to the slain civil rights leader.
"I know that people are going to hammer because they're going to say, 'It's no Martin Luther King speech,"' Beck told his radio listeners on Wednesday. "Of course it's not Martin Luther King. You think I'm Martin Luther King?"
And on Thursday, Beck repeated his claim that he didn't realize he was scheduling the event on the anniversary.
"I'm sorry, oh so important media, that I forgot the date," he said in a mocking tone. "It's not the date. It's the message."
Civil rights leaders said they hoped Beck wouldn't exploit the King legacy at the site. But the imagery - a crowd listening to a speaker standing in the shadow of Lincoln - was certain to draw comparisons.
"I hope that's not what he's trying to do. I hope that this is a coincidence," Jealous said. "But more than anything, I hope that he, having chosen this day and this locations, pushes himself to really honor the unifying legacy of Dr. King."