WASHINGTON – Bowing to a veto threat from President Bush and heavy pressure from its Republican leaders, the House on Thursday barely defeated an effort to scale back the USA Patriot Act, the controversial, administration-backed law to combat terrorism on the home front.

On a vote of 210 to 210 – a roll call that GOP leaders extended for more than 20 minutes to sway dissident Republicans – the House rejected an amendment that would have limited the Patriot Act by preventing the Justice Department from searching library and bookstore records to probe individuals’ reading habits.

The amendment was backed by an odd-bedfellows coalition of Democrats and conservative Republicans who believe the Patriot Act has gone too far in extending the federal government’s law enforcement powers. The act, which expanded the reach of law enforcement in the hunt for terrorists, was approved in the weeks after the Sept. 11 attacks.

The House appeared on track to pass the amendment when the 15 minutes traditionally allotted for a roll-call vote expired. But GOP leaders exercised their power to keep the vote open longer – as they did for far more time in November to pass the sweeping overhaul of the Medicare program.

About 10 Republicans who initially supported the amendment then switched their votes, allowing it to die on a tie vote and avoid an embarrassment to the Bush administration.

“Shame, shame, shame!” Democrats cried as the clock ticked and Republican votes were changed.

All California Republicans and Democratic Rep. Jane Harman of Venice voted against the proposal. Rep. Zoe Lofgren (D-San Jose) voted “present.” All other California Democrats voted in favor of the amendment.

At issue was one provision of the Patriot Act, the anti-terrorism law passed by huge bipartisan margins after the terrorist attacks on the World Trade Center and the Pentagon. The amendment would have blocked a section of the act that requires libraries, booksellers and others to release information about the reading habits of people under government investigation using a lesser standard of probable cause than is required under a normal criminal investigation.

The American Library Assn., which supported the amendment, has called that section of the act “a present danger to the constitutional rights and privacy rights of library users.”

The American Booksellers Assn. joined the ALA and the PEN American Center, a writers organization, in urging passage of the amendment.

After GOP leaders prevailed, the lead Republican advocate of the amendment, Rep. C.L. “Butch” Otter (R-Idaho), told reporters, “You win some, and some get stolen.”

The cliff-hanger vote was a measure of how tenuous Bush’s support is for extending, let alone expanding, the law enforcement powers of the Patriot Act in this election year.

Both liberal Democrats and conservative Republicans have worried about the government overreaching into private lives, and have joined in past efforts to roll back provisions of the Patriot Act.

Those initiatives have never made it into law, but neither have Bush’s efforts to expand the law’s reach.

The House amendment by Otter and Rep. Bernard Sanders of Vermont, the House’s only Independent, was offered to a $39.8-billion appropriations bill funding the Justice Department, the Commerce Department and the State Department. The debate came just as the administration was announcing an increased risk of terrorist attacks in the U.S. this summer and fall because of the November elections.

Supporters of the Patriot Act argued that surveillance programs were needed to help monitor terrorist activities.

“Lives have been saved, terrorists have been disrupted and our country is safer” because of the Patriot Act, said Rep. Porter J. Goss (R-Fla.), chairman of the House Permanent Select Committee on Intelligence.

Advocates of the amendment said that monitoring reading habits was an unnecessary intrusion into citizens’ privacy rights.

“Americans should have the right to read without fearing that Big Brother is looking over their shoulders and peeking into their personal lives to find out what they’ve been checking out of the library,” said Rep. Edward J. Markey (D-Mass.).

Bush has been trying to expand the government’s powers under the Patriot Act, and on Wednesday he had threatened to veto the appropriations bill if it included the bipartisan amendment to scale back the law.

The appropriations bill easily passed the House, 397 to 18, and now goes to the Senate, which is considering its own bipartisan proposal to scale back the powers of the Patriot Act.