A flurry of liberal and conservative groups issued last-minute pleas in the hours before the House Judiciary Committee prepared to vote on its latest version of a controversial intellectual property bill, known as the Stop Online Piracy Act.

“Join @reddit and PCCC (@BoldProgressive) in saving the Internet!” the Progressive Change Campaign Committee, a liberal advocacy group, tweeted urging followers to sign an online petition opposing the bill. The missive was paired with a letter signed by the founders of Twitter, YouTube and other tech giants.

Colin Hanna, the leader of the conservative group Let Freedom Ring, trumpeted the benefits of the legislation even as he noted it was a departure from Republicans’ anti-regulatory trope.

This is how Washington works. The high-profile battle over the anti-piracy bill that would give the Justice Department authority to target foreign websites selling counterfeit goods has pit tech giants like Google and Yahoo against the movie, music and pharmaceutical industries. Both sides have been spending big bucks on the issue for months and, with a key vote on the horizon, reached out to groups with long email lists of politically passionate supporters.

Let Freedom Ring has been in conversation with the U.S. Chamber of Commerce, which has been leading an aggressive campaign in support of the legislation since the summer. Hanna said the group has never received financial support from the chamber but acknowledged that one corporation involved with the copyright issue has cut LFR a check.

“That’s more coincidental than directly related to this issue,” he said.

Grover Norquist’s Americans for Tax Reform joined the fray, too, Wednesday, praising revisions to the bill intended to ease the burden on Internet Service Providers and payment processors.

Those interests say counterfeit items sold online result in billions of dollars of losses for American enterprises, cost U.S. jobs and are unsafe for consumers.

Internet giants such as Yahoo and Google oppose the bill.

Tumblr, Reddit, Mozilla, Union Square Ventures, Public Knowledge, MoveOn, the Wikimedia Foundation and the Center for Democracy & Technology are also trying to stymie the bill because, among other things, they say that, as written, it would lead to censorship of the Internet.

“We think it’s a do-or-die moment,” said David Segal, executive director of Demand Progress, which is part of the American Censorship Coalition. The group, which counts the American Civil Liberties Union and the American Federation of Teachers among its members, created an online tool to voluntarily censor their emails to raise awareness in advance of today’s vote.

“If we can prevent passage out of House Judiciary or get them to amend it … then I think there’s a good chance we’ll see what we want in the long run,” he told Roll Call. “We’re just trying to drive an extraordinary number of constituent contacts.

Sen. Ron Wyden (D-Ore.) has placed a hold on companion legislation in the Senate and is expected to drop an alternative bill that would delegate piracy enforcement to the International Trade Commission.

Correction, Dec. 15

An earlier version of this story mentioned the wrong Congressional chamber when referencing the upcoming Stop Online Piracy Act vote.