Congressional support for controversial online piracy legislation eroded dramatically on Wednesday in the face of an unprecedented online protest supported by tech titans such as Google, Wikipedia and Facebook. 

Several key senators withdrew their support from the Senate’s Protect IP Act (PIPA), including Tea Party favorite Sen. Marco Rubio (R-Fla.) and Sen. Roy Blunt (R-Mo.), an elected member of his party’s leadership. 

Sen. John Cornyn (R-Texas), who leads the Senate GOP’s campaign team, said the legislation should be put on hold, while Sen. Orrin Hatch (R-Utah), a sponsor and the ranking member of the Senate Finance Committee, retreated from the bill. Sen. John Boozman (R-Ark.) also withdrew his sponsorship.

{mosads}Thousands of websites went dark on Wednesday to protest the two Internet piracy bills, the House’s Stop Online Piracy Act (SOPA) and the Senate’s PIPA. At least two California Democrats, Reps. Anna Eshoo and Zoe Lofgren, joined the protests by blacking out their websites.

Sen. Jim DeMint (R-S.C.), a leader of Senate conservatives, also came out against the bills, calling them “misguided bills that will cause more harm than good.”

“When protecting intellectual property rights, we must not undermine free speech, threaten economic growth, or impose burdensome regulations,” DeMint tweeted.

Opposition is also building in the House. Two of the original Republican co-sponsors of SOPA, Reps. Ben Quayle (Ariz.) and Lee Terry (Neb.), withdrew their support Tuesday before the protests began, and scores of other lawmakers took to Twitter Wednesday to affirm their opposition.

The coordinated online protests are aimed at bringing down legislation that would empower the Justice Department and copyright holders to demand that search engines delete links to sites deemed to be “dedicated” to copyright infringement. Ad networks and payment processors would be prohibited from doing business with the sites.

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Where the protests left the legislation, which is supported by the Motion Picture Association of America and recording industry, among other groups, is unclear. The Senate is scheduled to hold a procedural vote on the legislation next week, but it is uncertain whether the 60 votes to move forward can be found. The fight over the bills has broken across party lines, with House Oversight and Government Reform Chairman Darrell Issa (R-Calif.) leading opposition in the House against Rep. Lamar Smith (R-Texas), the chairman of the House Judiciary Committee.

Hundreds of millions of Internet users, most of whom might have been unaware of the bills until Wednesday, are likely to have noticed the protests. 

Google, the most visited site in the world, plastered a black box evoking censorship over its logo and claimed the bills would “censor the Web and impose harmful regulations on American businesses.” Users who click on the black box are re-directed to a petition urging Congress to drop the piracy legislation on a page.

Wikipedia — the world’s sixth most popular site, according to the Web firm Alexa — went a step further, shutting down its English-language site entirely. Visitors to Wikipedia are greeted with a minimalistic, dark page with the headline: “Imagine a world without free knowledge.” 

After announcing he was withdrawing his support, Rubio said Congress should take its time in crafting new legislation that addresses the concerns raised by both the technology and content industries. 

“I have been a co-sponsor of the PROTECT IP Act because I believe it’s important to protect American ingenuity, ideas and jobs from being stolen through Internet piracy, much of it occurring overseas through rogue websites in China,” Rubio said in a post on Facebook. “As a senator from Florida, a state with a large presence of artists, creators and businesses connected to the creation of intellectual property, I have a strong interest in stopping online piracy that costs Florida jobs.

“However,” he continued, “we must do this while simultaneously promoting an open, dynamic Internet environment that is ripe for innovation and promotes new technologies.”

Six other GOP senators wrote to Senate Majority Leader Harry Reid (D-Nev.) last week asking him delay a vote on PIPA scheduled for next week, but a senior Democratic aide told The Hill Reid plans to press ahead with the vote after requesting some changes to the Domain Name Service provision from sponsor and Judiciary Chairman Patrick Leahy (D-Vt.).

Google and Wikipedia weren’t the only big-name sites slamming the bills. The popular discussion board reddit went dark at 8:00 a.m., posting a message that read: “SOPA and PIPA damage the Internet. Today we fight back.” 

Reddit encouraged users to “take today as a day of focus and action to learn about these destructive bills and do what you can to prevent them from becoming reality.”

Wired, a technology magazine, also joined in, blacking out the headlines on its website. 

Facebook did not shut down, but the social network’s Washington, D.C., office posted a page that said the bills are “not the right solution” because of the “collateral damage they would cause to the Internet.”

Other sites participating in the protest include craigslist, Mozilla, Imgur, Raw Story, MoveOn.org, Cheezburger and the Consumer Electronics Association.

The protests seemed to piquing the interest of Web users Wednesday. By mid-morning, “SOPA” and “SOPA blackout” were among the top 10 trending search terms on Google.

The bills’ sponsors dismissed the protests Tuesday.

Smith, who authored SOPA, called Wikipedia’s protest a “publicity stunt” that promotes “fear instead of facts.”

“Perhaps during the blackout, Internet users can look elsewhere for an accurate definition of online piracy,” he said.

Leahy, the chief author of the Senate bill, said the protest is based on a misunderstanding of the legislation.

“The PROTECT IP Act will not affect Wikipedia, will not affect reddit, and will not affect any website that has any legitimate use,” he said.

“Perhaps if these companies would participate constructively, they could point to what in the actual legislation they contend threatens their websites, and then we could dispel their misunderstandings. That is what debate on legislation is intended to do, to fine-tune the bill to confront the problem of stealing while protecting against unintended consequences.”

Movie studios, record labels and business groups say piracy legislation is needed to stop the illegal downloading of movies, music and other copyrighted content, and argue that legislative action is long overdue. 

But consumer groups and Web companies warn the bills would stifle innovation and censor free speech. They say the legislation would impose an unreasonable burden on websites to police user-generated content and could lead to legitimate websites getting shut down.

The Motion Picture Association of America called the protests an “abuse of power” aimed at turning Web users into “corporate pawns.”

“A so-called ‘blackout’ is yet another gimmick, albeit a dangerous one, designed to punish elected and administration officials who are working diligently to protect American jobs from foreign criminals,” MPAA Chairman and former Sen. Chris Dodd (D-Conn.) said in a statement. “It is our hope that the White House and the Congress will call on those who intend to stage this ‘blackout’ to stop the hyperbole and PR stunts and engage in meaningful efforts to combat piracy.”

The Senate is set to vote on the legislation on Tuesday. Smith has said he will push ahead with the House’s version in the Judiciary Committee next month.

—This story was first posted at 7:35 a.m. and was last updated at 2:56 p.m.