A diverse group will gather near the U.S. Capitol on Saturday to denounce the government's dragnet phone and Internet surveillance programs revealed in June by whistle-blower Edward Snowden.

The date is the 12th anniversary of President George W. Bush signing into law the USA Patriot Act, which with approval from the Foreign Intelligence Surveillance Court allowed years of hushed data collection by the National Security Agency.

"We're expecting this to be the largest privacy-related rally – potentially – in U.S. history," said Evan Greer, campaign manager of Fight for the Future, an Internet policy group that's helping organize the event. "We are expecting thousands of people to come out to D.C. The rally has been endorsed by over a hundred organizations, from the far left to the far right."

Among the event sponsors are the American Civil Liberties Union, the Electronic Frontier Foundation, the Mozilla Foundation, the Green Party, the Libertarian Party, social news website Reddit, the Council on American-Islamic Relations, Demand Progress and Students for Liberty.

"It's exciting to see so many different groups coming together... groups that normally never would be sitting in the same room or at the same rally are working together on this issue," Greer said. "This is an incredibly politically diverse coalition uniting around the issue of government surveillance and recognizing the threat that it poses to our most basic rights, like freedom of speech, freedom of expression and privacy."

Rally participants will gather near Union Station at noon before walking a short distance to the reflecting pool in front of Congress. The musical group YACHT will provide live entertainment and Reddit co-founder Alexis Ohanian, NSA whistle-blower Thomas Drake, former Gov. Gary Johnson, R-N.M., and author Naomi Wolf will give speeches.

"The diversity of this coalition should surprise no one: freedom and privacy are fundamental American values that transcend the left-right divide," said Michelle Richardson, legislative counsel at the ACLU's Washington office, in a released September statement.

The NSA's surveillance programs are supported by President Barack Obama and are unlikely to be easily undone. Despite presidential approval, members of the House of Representatives fell just 12 votes short of advancing legislation to eliminate one program – the collection of all Americans' phone records – on July 24. At least two congressmen have reversed their positions since that vote.

Patriot Act author Rep. Jim Sensenbrenner, R-Wis., announced Oct. 9 he will be pushing for a so-called "Freedom Act" to curtail the NSA programs, which he believes were improperly permitted by secret court decisions. Rep. Justin Amash, R-Mich., has also announced plans for future votes against the programs.

Electronic Frontier Foundation Activism Director Rainey Reitman is flying in from California with five or six EFF colleagues for the weekend. EFF is helping to set up meetings on Friday between anti-surveillance constituents and either congressional staffers or targeted congressmen themselves.

EFF has a target list of politicians who previously voted against NSA-enabling Foreign Intelligence Surveillance Act amendments, but who are now supporting the NSA programs.

"Folks like Al Franken, who for whatever reason are not voting in a pro-civil liberties fashion on this particular issue now – we're going to try to use this as an opportunity to get citizens and taxpayers in front of them to confront them with the fact that this is a huge issue for everyday Americans," Reitman said. "We have a nice chart of people. ... Nancy Pelosi is on our target list, but she's going to be a tough nut to crack."

It's unclear if sympathetic congressmen will show up Saturday, but organizers say around 3,500 people have RSVP-ed online at rally.stopwatching.us. More than $33,000 was raised via the crowd-funding site indiegogo to subsidize bus trips from nearby cities and a corresponding petition that will be on display Saturday has attracted 575,000 signatures.

Watch: A promotional video released by organizers: