The House vote to block NSA funding for one of its data collection programmes is the biggest manifestation yet of a revolt that has steadily grown over the last two months.

When the Guardian and Washington Post first revealed the documents leaked by former NSA contractor Edward Snowden, there were relatively few in Congress prepared openly to challenge the government over intrusions into privacy.

The challenge was largely restricted to the two long-term sceptics, senators Ron Wyden and Mark Udall. This left Barack Obama able to claim that the surveillance was not secret because every member of Congress had been briefed about it, and that every piece of legislation since 2006 related to it had been passed with large bipartisan majorities.

Towards the end of June, opposition to the surveillance programme began to grow. Wyden and Udall were joined by 24 other senators to send a joint letter to to intelligence chiefs complaining about a secret body of laws and misleading statements by officials.

At a House judiciary hearing last week, member after member said that while they had little sympathy for Snowden, they were glad about the revelations and repeatedly challenged the NSA and justice department officials at the hearing.

The scheduled House vote brings together a potent combination of progressive Democrats and libertarian Republicans. Such is the strength of feeling that they are prepared to defy not only pleas from the White House and personal appearances on the Hill by intelligence chiefs, but their own congressional leaders.

The very fact that the vote was to be held enraged the Wall Street Journal, which, in an editorial, wrote: "Few things are more dangerous than Congress in heat, and so it is this week as a libertarian-left wing coalition in the House of Representatives is rushing to neuter one of the National Security Agency's anti- terror surveillance programs."

It added: "The last thing Congress should do is kill a program in a rush to honor the reckless claims of Mr Snowden and his apologists."

Congress is due to begin a five-week recess at the start of August, and much of the momentum will go out off the issue, at least on the Hill. But there will be more hearings in in the autumn, and more votes. Proposed reform of the Patriot Act, which authorises much of the surveillance, has already been introduced. One of the changes would require the government to demonstrate a clear link to terrorism or spying before being allowed to collect Americans' private information.

Changes are also proposed to reform the ultra-secret Fisa court, which issues warrants for surveillance. Many members of Congress vote because they regard such issues as a matter of principle but others are also motivated by pressure from voters.

Wyden mentioned this on Tuesday in speech in Washington, saying Americans were stunned by the scale of the surveillance. "And, boy, are they angry. You hear it in the lunchrooms, town hall meetings and senior citizen centres," Wyden said.

And the public will almost certainly be still engaged in that debate when Congress returns in September. A Washington Post/ABC News poll published Wednesday showed concerns about personal privacy have grown. The poll suggested about three-quarters of Americans see the NSA programmes as infringing on their rights to privacy.

In the aftermath of 9/11, when there was overwhelming concern over security, the balance has gradually shifted, with the poll finding 57% in favour of unfettered investigations and 39% seeing protection of privacy as the more important.

There will likely be more disclosures in the media that will keep the debate alive. And legal actions are pending. A preliminary court hearing is scheduled for Thursday in New York at which the American Civil Liberties Union is challenging the constitutionality of the NSA's mass collection of phone records. The ACLU said it will be the first time that the government has been forced to address NSA surveillance in court.

All this puts pressure on the White House to act. The Obama administration responds that it has already made gestures but these are so minor and modest they have made little impact on public consciousness. Big concessions will be required to allay public concerns.

The growing revolt helps Snowden. The Washington Post/ABC News poll shows a drop in public support for him, with 53% saying he should be charged with a crime for his leaks against 43% less than a month ago. But the debate he started can only help him if he is ever arrives back on US soil. Given the debate he has started, it makes it harder for the justice department to argue that he is not a whistleblower,

For the moment, Snowden is at the mercy of the Russian authorities, possibly doomed to a life of exile there unless they relent and allow him to leave for Latin America – assuming a way can be found for him to get there avoiding US attempts to intercept him.

But he can at least have the satisfaction of feeling that the revolt has vindicated the disclosures he made in Hong Kong.