WASHINGTON » Democrats quickly enjoyed the first fruits of a milestone Senate vote making it harder for the Republican minority to block President Barack Obama’s nominations: They swiftly ended a GOP filibuster against one of his top judicial selections and prepared to do the same for two others.

Over the longer term, they might regret what they did and how they did it, Republicans and others are warning.

When Democrats muscled the changes through Thursday over the opposition of every GOP senator, it helped heighten Congress’ already high level of partisan animosity. Senate Majority Leader Harry Reid, D-Nev., used a process that let Democrats unilaterally weaken the filibuster by simple majority vote, rather than the two-thirds margin usually used for major changes in chamber rules, which would have required GOP support.

"If the majority can change the rules, then there are no rules," said veteran Sen. John McCain, R-Ariz., 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," Senate Minority Leader Mitch McConnell, R-Ky., 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."

McConnell spoke after the Senate voted 52-48 to allow a simple majority vote to end filibusters, instead of the 60 votes required since 1975. The change affects nominees for top federal agency and judicial appointments, but not Supreme Court justices.

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 GOP 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 Iowa 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.

"The tyranny of the majority. That’s what it’s going to be" at some point in the future, predicted Steve Bell, a former top Senate Republican aide who is now a senior director at the Bipartisan Policy Center, which advocates partisan cooperation.

Democrats said GOP delays had gone too far, blocking nominees not for their qualifications or ideology but for political reasons like preventing too many Democrats from serving on a court.

Republicans argued that Democrats have acted similarly to block appointments by GOP presidents and warned they would use Senate rules to their advantage whenever they win control of the chamber.

"We understand all the considerations," Reid said of the risks. "But let’s be realistic. What could they do more to slow down the country? What could they do more than what they’ve already done to stop the Senate from legislating?"

"We’d much prefer the risk of up-or-down votes and majority rule than the risk of continued total obstruction," said New York Sen. Chuck Schumer, the No. 3 Senate Democratic leader.

Immediately after the showdown roll call, senators voted to end GOP 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.

December votes were also planned on District Judge Robert L. Wilkins and law professor Cornelia Pillard, two other Obama choices Republicans had blocked for the D.C. Circuit. That will give judges picked by Democratic presidents a 7-4 edge over those selected by Republicans for that court.

Labor and liberal groups hailed the filibuster curbs, expressing satisfaction that Democrats had finally stood up to the GOP.

"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."

But Sen. Carl Levin of Michigan, one of three Democrats who voted against diluting the filibuster, noted that past Democratic minorities have used the procedure to block GOP moves to limit abortion rights and repeal the estate tax.

He said he feared that a future Senate majority would weaken filibusters against legislation and "down the road, the hard-won protections and benefits for our people’s health and welfare will be lost."

Associated Press writer Henry C. Jackson contributed to this report.