WASHINGTON -- When Fox News and talk-radio host Glenn Beck comes to Washington this weekend to headline a rally intended to "restore honor" to America, he will test the strength -- and potentially expose the weaknesses -- of a conservative, grass-roots movement that remains an unpredictable force in the country's politics.

Beck, who is admired and assailed for his faith-based patriotism and his brash criticism of President Barack Obama, plans in part to celebrate Martin Luther King Jr. as an American hero. He will speak on the anniversary of the "I Have a Dream" speech, from the spot where King delivered it.

In Charleston and in countless other towns and cities, tea party supporters will be piling into tour buses and setting out today and Saturday for Washington. Beck, on his website, said the event is neither political nor affiliated with the tea party, but tea party followers may disagree.

Some tea party activists said the event, at which former Alaska Gov. Sarah Palin also is scheduled to speak, will have a greater impact than last September's "9/12" march along Pennsylvania Avenue.

Though the attendance figures for that anti-tax rally are disputed, it was the first national gathering to demonstrate the size and influence of the tea party movement.

"We had done this last year, so we decided to do it again," said Joanne Jones with the Charleston Tea Party. "Obviously, with Palin, there's a certain connection to politics, but the people I've talked to, I would say they're concerned with the direction the country is taking, and I think they're showing up to let the political elites know that they're very unhappy and will be heard in November.

"If you take away party politics and talk about people leading responsible lives, I think that's a lot of what Beck's talking about," she said. "None of that needs to be political."

Charleston Fox News radio affiliate 94.3 WSC-FM has been promoting the event -- Beck and Palin are Fox commentators -- and will provide a send-off for the six busloads of people the Charleston Tea Party organized for the trip.

Basic questions linger about the rally, including how big it will be and whether the event will help or hurt Republicans in November. Also unanswered is whether Beck can pull off the connection to King without creating offense, or without confrontation with another event the same day led by the Rev. Al Sharpton.

Beck said he did not intentionally choose the "I Have a Dream" anniversary for his rally, but he said in a recent broadcast that he thinks the coincidence is "divine providence."

"Whites don't own Abraham Lincoln," he said. "Blacks don't own Martin Luther King. Those are American icons, American ideas, and we should just talk about character, and that's really what this event is about. It's about honoring character."

The rally will be on the steps of the Lincoln Memorial.

It will be a weekend of political activity, with tea party organizer FreedomWorks hosting a convention in Washington today, Beck's and Sharpton's events Saturday, and a major effort by Democrats to knock on 200,000 doors nationwide Saturday and Sunday.

Sharpton's annual commemoration of the "Dream" speech will begin with speeches at a high school and will continue with a march to the site of the planned King memorial, at the same end of the Mall as the Lincoln Memorial, placing participants of both events in close proximity.

Beck said his event, "Restoring Honor," is not intended to rally voters to the polls in November's midterm elections. No signs are allowed, and not one elected official currently in office will be part of the program.

Operatives at virtually every Republican committee in Washington claimed little or no knowledge of the event.

They may well have cause to be squeamish. Beck has accused Obama of reverse racism and of having "a deep-seated hatred of white people," and Beck's plan to celebrate the lessons of the civil rights era creates the possibility of confrontations.

"In general, people coming to Washington, being organized and active is a good thing," said Doug Heye, a spokesman for Republican National Committee Chairman Michael Steele. "But I don't know about any Glenn Beck event."

Conservative activists, meanwhile, promise that the rally will show their unity and voice. Jones said the Charleston Tea Party sold out six buses and couldn't arrange for more. "We've had to turn people away," she said. "Buses were in great demand."

Sharpton, meanwhile, is expecting thousands of participants. Spokeswoman Rachel Noerdlinger noted that Sharpton decided in April that his group's annual commemoration of King's speech would be in Washington this year, and she stressed that it is not in response to the Beck event.

Sharpton argues that Beck's message is counter to King's. "Glenn Beck and others are expected to push for the expansion of states' rights, the exact antithesis of the civil rights movement and Dr. King's legacy," Sharpton said in a news release promoting his march.

"The tea party and allied conservatives are trying to break that national stance on justice and, in turn, break the crux of what the civil rights movement symbolized and what Dr. King fought and literally died for."