Hatch was one of six GOP senators to write to Senate Majority Leader Harry Reid (D-Nev.) last week, urging him to delay the vote on the bill.
Sen. Chuck Grassley (R-Iowa) also signed the letter, but he is still listed as a co-sponsor of the legislation. A spokeswoman for Grassley said the senator is "troubled" by provisions in the bill that "could adversely impact cybersecurity and the First Amendment," but did not clarify whether he will formally withdraw his support.
Grassley is the ranking Republican on the Senate Judiciary Committee, which unanimously approved the legislation in May. Hatch is the ranking Republican on the Senate Finance Committee and also serves on the Judiciary Committee.
The Protect IP Act and its House counterpart, the Stop Online Piracy Act (SOPA), are designed to go after foreign websites that offer illegal copies of movies, songs and TV shows with impunity. The bills 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.
Movie studios, record labels and business groups say legislation is needed to curb online copyright infringement, which is hurting businesses and eliminating jobs.
But on Wednesday, thousands of websites, including Wikipedia, Google and reddit, staged a massive protest against the legislation.
The English version of Wikipedia shut down entirely, redirecting users to a page criticizing the legislation.
Google, the most visited site in the world, placed a black box over its logo. Users who click on the box are sent to a petition claiming the bills would "censor the Web and impose harmful regulations on American businesses."
The Senate is expected to vote on the legislation on Tuesday.