Republicans argued that Democrats have acted similarly to block appointments by Republican presidents and warned they would use Senate rules to their advantage whenever they win control of the chamber.
"If the majority can change the rules, then there are no rules," said veteran Republican Sen. John McCain, who has resisted similar changes in the past. "It puts a chill on the entire U.S. Senate."
Such comments suggested a further erosion in the mutual trust the two parties would need to tackle sensitive, large-scale issues like still-massive budget deficits and a tax system overhaul. The tensions also won't help Congress' efforts early next year to avoid another government shutdown and prevent a federal default, twin disputes that the two parties struggled to resolve this fall.
And even though Thursday's change left intact the 60 Senate votes needed to filibuster, or delay, legislation, it raised an obvious question: Might a future Senate majority, hitting obstacles advancing a president's agenda, ram through changes weakening filibusters against bills too?
In control of both the White House and Congress someday, Senate Republicans might be tempted to force a filibuster change to cover legislation and use it, for example, to repeal Obama's health care law.
"I don't think this is a time to be talking about reprisals," Republican Senate Minority Leader Mitch McConnell said after the vote. He said later, "The solution to this problem is at the ballot box. We look forward to having a great election in November 2014."
Republicans had warned repeatedly that should they win Senate control, they will happily use the diluted filibuster to win Senate approval for future nominees by Republican presidents that under past standards Democrats might have blocked.
"The silver lining is that there will come a day when the roles are reversed," said Sen. Charles Grassley, top Republican on the Senate Judiciary Committee. He warned that when his party wins a Senate majority they likely will apply the 51-vote filibuster threshold to a Republican president's Supreme Court nominees.
Immediately after the showdown roll call, senators voted to end Republican delays against attorney Patricia Millett, whom Obama wants to fill one of three vacancies at the U.S. Court of Appeals for the District of Columbia Circuit. The powerful court has jurisdiction over White House and federal agency actions.
Millett will be formally confirmed after the Senate returns from a two-week Thanksgiving recess.
Labor and liberal groups hailed the filibuster curbs, expressing satisfaction that Democrats had finally stood up to the Republican.
"There was no choice," said Nan Aron, president of the liberal coalition Alliance for Justice. "The Republican minority had turned the existing rules into weapons of mass obstruction."
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Associated Press writers Alan Fram and Henry C. Jackson contributed to this report.
