As websites went dark and picketers gathered in front of lawmakers' offices, support for anti-piracy legislation eroded on Wednesday, raising doubts about its viability when it is scheduled for a key Senate vote next week.

Meanwhile, Vice President Joseph Biden was to meet with Silicon Valley and Hollywood leaders in meetings Wednesday evening in San Francisco and on Thursday in Los Angeles, where the acrimony over the proposed bills has sharply divided the communities.

In one of the most significant blows to the prospects for the Protect IP Act, Sen. Orrin Hatch (R-Utah) announced Wednesday that he was withdrawing his support. As a senior member of the Senate Judiciary Committee, he was one of the key sponsors of the legislation when it passed the committee unanimously in May. But he said in a Twitter message: "After listening to the concerns on both sides of the debate over the Protect IP Act, it is simply not ready for prime time."

In addition, Sen. Marco Rubio (R-Fla.), Sen. John Cornyn (R-Texas) and Sen. Roy Blunt (R-Mo.) each said they were withdrawing their support. In the House, Speaker John Boehner indicated that the House version, the Stop Online Piracy Act, would not come to a floor vote anytime soon, citing a lack of consensus. Rep. Ben Quayle (R-Arizona) was among a handful of members to back away from the legislation.

The shutdown of websites Wednesday included Wikipedia, Reddit and Wordpress. Google blacked out its logo, and other sites including Craigslist featured a prominent message against the legislation.

Senate Judiciary Committee chairman Patrick Leahy (D-Vt.) has been organizing representatives from various industries on the different sides of the issue to work out a compromise, but there was little indication that anything was imminent.

In Manhattan, hundreds of protesters turned out to cheer on speakers from Silicon Alley outside the Midtown offices of New York Sens. Chuck Schumer and Kirsten Gillibrand, where techies and well-wishers chanted anti-SOPA/PIPA slogans.

"The Stop Online Piracy Act will not actually do much to stop online piracy," said NYU teacher and "Cognitive Surplus" author Clay Shirky, who proposed that the name of the legislation be changed to the First Amendment Sunset Act. "You can't just shut people up if you don't like what they're saying," he told the cheering aud.

The industry lobby scrambled to shore up support. A coalition of industry guilds including SAG, AFTRA, the American Federation of Musicians, IATSE, Teamsters and the Directors Guild sent a letter to Gillibrand and Schumer. "We know the pressure you are getting to renege on your commitment," they said.

They added that "despite all the noise, it must be noted that these opposition voices represent relatively few American workers. Google, for instance, employed just 31,000 people worldwide in 2011 while our guilds and unions alone collectively represent over 400,000 members of the entertainment community."

While a showbiz-financed group called Creative America launched a new series of ads Wednesday, including a billboard in Times Square, what has been striking is the lack of prominent industry figures promoting the legislation, compared to the array of bloggers, Internet entrepreneurs and public interest advocates waging a war against it. In fact, some popular stars like Ashton Kutcher and Alec Baldwin tweeted their opposition to the legislation, while filmmaker Michael Moore shut down his site in solidarity with others across the web.

Biden's meeting was with a host of Silicon Valley leaders as well as DreamWorks Animtation CEO Jeffrey Katzenberg. Biden will visit Los Angeles on Thursday, where he is expected to host another meeting with business executives expected to include studio officials.

The meetings have been in the works for several weeks, before the debate over the anti-piracy bills escalated and the White House released a statement critical of some of the provisions. But Biden has been a point person within the administration on copyright issues, and has hosted several gatherings at the White House with studio executives and recording industry reps.

Those expected at Wednesday's meetings were Apple's Tim Cook, Netflix's Reed Hastings, Katzenberg, Zynga's Mark Pincus, Symantec's Enrique Salem, Facebook's Sheryl Sandberg, Google's Eric Schmidt, Yahoo's Scott Thompson and Laura Tyson of UC Berkeley.

The Gotham protest was still was a far cry from the raucous crowds that gathered a few months ago for the Occupy Wall Street demonstrations. A sense of calm prevailed, with protesters mostly refraining from chanting too loudly, and a few police herding compliant onlookers into well-maintained protest zones. Third Avenue was blocked off between 48th and 49th streets to allow for the protest.

The speeches, however, were rousing: Hollywood took its lumps at the rally, organized by the networking org New York Tech Meetup. One placard read "Pander to the people, not Hollywood;" another had a picture of a cat holding the Bill of Rights and the slogan "I can has freedom?"

"When Hollywood lobbyists show up with $94 million as they did last year, both Democrats and Republicans line up," said Reddit co-founder Alexis Ohanian.

MoveOn.org's Eli Pariser was even more adamant: "You have groups like MoveOn all the way over to groups like (conservative coalition) Red State who think this is a bad idea," he said. "The only people who think this is a good idea are the crumbling old legacy media who want to go back to VHS tapes and CDs, and congresspeople."

Contact Ted Johnson at ted.johnson@variety.com