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Sen. Robert Byrd, the dean of the Senate and its resident constitutional expert, counts only a few regrets in his 48-year Senate career: filibustering the 1964 Civil Rights Act, voting to expand the Vietnam War, deregulating airlines.

Add to the list a new one from this century: supporting the anti-terror USA Patriot Act after the Sept. 11, 2001, attacks.

"The original Patriot Act is a case study in the perils of speed, herd instinct and lack of vigilance when it comes to legislating in times of crisis," the West Virginia Democrat said Monday on the eve of the Senate's final votes on its renewal. "The Congress was stampeded, and the values of freedom, justice and equality received a trampling in the headlong rush."

This week as he embarks on a re-election campaign for a record ninth term, Byrd, 88, will vote "no" on renewing 16 major provisions of the act due to expire March 10. He argues that even with new privacy protections added this year by the Bush administration and its allies, the law has given the government too much power to pry.

"This new proposal would erase too many of our freedoms guaranteed to the American people," Byrd added in a statement to The Associated Press. "In essence, this legislation says that the Bill of Rights is right no more."

His position allies him with Sen. Russell Feingold, a relative Senate newcomer who nonetheless foresaw potential problems with the original Patriot Act before Byrd or any other member of the Senate. In 2001, Feingold, D-Wis., cast the lone vote against the new terror-fighting law.

"I wish I had voted as he did," Byrd lamented on the Senate floor.

Now, with a long list of complaints against what he says are the Bush administration's overreaching on the war on terror — including a controversial eavesdropping program by the National Security Agency— Byrd is siding with Feingold against the Patriot Act.

"Ben Franklin, that wise man among the Constitution's framers, perhaps said it most simply," Byrd says now. "'Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety."'

Those who support the bill acknowledge lingering civil liberties concerns, including its sponsor, Senate Judiciary Committee Chairman Arlen Specter, R-Pa. But they argue that the compromise legislation, even flawed, holds the best chance of renewing the law because the House is willing to pass it. Without such accord, Congress would end up extending the existing law repeatedly or let it expire.

Specter is looking to strengthen the act's civil liberties protections further by introducing legislation Tuesday to restore several provisions contained in a Senate bill unanimously passed last year and rejected by the House. The measure would make several changes, including one requiring law enforcement officials to notify the target of a secret search warrant within seven days of the search, rather than the 30 days included in the compromise. Specter said he will convene hearings on his bill next month.

For his part, Bush argues that the bill now before Congress strikes the right balance between personal freedoms and a muscular war on terror in an age when the nation is squarely in al-Qaida's crosshairs.

Byrd is one of two senators who stuck with Feingold against the bill as the opposition first grew large enough last year to block the measure — then shrank after the Bush administration and key Senate Republicans struck a deal to strengthen the rights of people targeted in government terror probes.

On a 96-3 test vote earlier this month, Byrd, Feingold and Sen. Jim Jeffords, I-Vt., were the only dissenters.

A few senators planned to use a second test vote Tuesday to protest the majority Republicans' refusal to allow amendments. Senate Minority Leader Harry Reid, D-Nev., and Sen. Patrick Leahy, D-Vt., for example, planned to vote "no" with Byrd and Feingold on Tuesday, but "yes" for the bill's final passage Wednesday. The House was expected to consider the Patriot Act renewal later in the week.

With his white mane and weighty presence, Byrd typically commands great deference from colleagues of both parties. That's because Byrd literally wrote the book on the Senate, a four-volume history. He is fond of declaring that that he loves the institution more than its members. Sponsors of contentious bills often find themselves confronted with one or another "Byrd problem" — shorthand for procedural concerns raised by the senior senator from West Virginia.

Byrd's reversal on the Patriot Act on procedural and constitutional grounds dovetails with his growing opposition to the Bush administration's handling of the war on terrorism.

He tried to block the creation of the Homeland Security Department, which he said would give too much authority to the president. He voted against the war in Iraq.

And in 2004, Byrd published a book that minced no words. In "Losing America: Confronting a Reckless and Arrogant Presidency," Byrd blasted his colleagues for failing to challenge Bush's polices and expanding executive power.

As for changing sides, Byrd's got a favorite phrase, from the poet James Russell Lowell:

"The foolish and the dead alone never change their opinions."