On Thursday the House passed a bill aimed at reforming the National Security Agency's bulk collection of domestic phone records in a 303-to-121 vote. But the version of that bill, known as the USA Freedom Act, was different from the one that was recently approved by the House Intelligence and Judiciary Committees. The new version from the House Rules Committee, privacy advocates say, significantly weakened the reform and included loopholes that could potentially allow bulk data collection on U.S. citizens to continue.

Privacy advocates weren't the only ones upset about the changes. Many co-sponsors of the original version were also concerned. In fact, a Washington Post analysis of the votes shows that 76 of the 152 co-sponsors of the earlier version voted against passage of the altered version on the House floor Thursday. So, half of the co-sponsors ended up voting against what was supposed to be their own NSA reform bill.

That includes Rep. Jared Polis, (D-Colo.), who released a press statement about his change of heart after the vote. “Unfortunately, the USA Freedom Act, which I cosponsored as introduced, has been watered down and co-opted to the point that it creates the possibility that NSA could misuse the bill- contrary to the legislative intent- to conduct broad searches of communication records," Polis said.

The White House came out in support of the bill on Wednesday. But many privacy advocates and a coalition of technology companies dropped their support in light of the changes made to the bill. A blog post from Kevin Bankston, the policy director at the New America Foundation's Open Technology Institute, laid out some areas of concern for the groups. Those include changes that they say broaden the search selector terms used by the NSA to define the scope of data requests from phone companies in such a way that could still allow bulk collection and that could limit the transparency reporting for companies who receive such requests.

"The last-minute changes made to the USA Freedom Act substantially weakened its intended reforms," says Amie Stepanovich, senior policy counsel at Internet freedom group Access, which pulled its support of the bill Tuesday. "The corresponding shift in support from the bill's co-sponsors demonstrates that, in its current form, USA Freedom Act no longer goes far enough to protect user rights."

Still, some civil liberties advocates see the House passage of the bill as a positive step.“While far from perfect, this bill is an unambiguous statement of congressional intent to rein in the out-of-control NSA," said Laura W. Murphy, director of the American Civil Liberties Union's Washington legislative office.

Murphy said the group shared many of the same concerns about the bill not going far enough to protect users. But without the bill, she said, other options could be no reform at all or a bill that actually codifies the bulk collection of phone records. Murphy also said the fight isn't over, noting that the group will "fight to secure additional improvements in the Senate.”

Stepanovich, too, sees the Senate as the next fight, saying she hopes those lawmakers see the discontent among House sponsors of the original bill as "evidence that broad support still exists for them to pass a stronger bill that defies the administration's last-minute attempts to subvert these necessary checks to NSA spying."

And some already appear ready for a fight, including longtime surveillance skeptic Sen. Mark Udall (D-Colo.). "The House-passed USA Freedom Act bears little resemblance to the bicameral and bipartisan legislation that I supported months ago and that I still support," he said in a statement Thursday afternoon. "The Senate must take up the original USA Freedom Act — which clearly ends bulk collection and which includes more aggressive steps to protect Americans' privacy, such as important provisions to safeguard Americans from warrantless, backdoor searches of their private communications."

During floor speeches before Thursday's vote, several supporters of the altered version acknowledged it did not include everything they'd hoped for, but still urged their colleagues to vote for the measure. Rep Jim Sensenbrenner (R-Wis.) who was the primary sponsor of the bill told fellow members, "Don't let the perfect be the enemy of the good."