Republicans are poised to repeal a U.S. Senate rule that allows minority-party Democrats to block confirmation of Supreme Court nominees, including President Donald Trump's choice of Neil Gorsuch for the lifetime post.
The expected rule change, amid deepening partisanship in a chamber known as "the world's greatest deliberative body," is raising questions over whether there could be a future move to prohibit "filibusters" on legislation.
Here is how the filibuster has been used and what curtailing it could mean:
WHAT IS A FILIBUSTER?
It is a procedural move, often by a minority of senators, to block legislation or Supreme Court nominations that typically enjoy the support of majority-party senators, in this case, Republicans.
According to Senate historians, "filibuster" comes from a Dutch word meaning "pirate."
The practice became popular in the 1850s and was also used by House of Representatives members, until that body became so large with an expanding U.S. population as to require stricter rules governing floor debates.
Senate Democrats have gathered more than the 41 votes they need in the 100-seat chamber to mount a filibuster against Gorsuch, a conservative appeals court judge.
WHAT DOES GEORGE WASHINGTON HAVE TO DO WITH FILIBUSTERS?
The first U.S. president is said to have observed that the Senate was created to cool legislation from the hot-tempered House just as a saucer was used to cool hot tea. The filibuster is just such a coolant.
HOW IT WORKS
When a bill or Supreme Court nomination hits the Senate floor, senators who oppose it can talk until at least 60 senators band together to limit debate. That gives a minority of senators huge power. If a bill or a nomination fails to draw the needed 60 votes, it is effectively killed.
The all-time record for a Senate filibuster speech - 24 hours, 18 minutes - was set by the late segregationist Senator Strom Thurmond, who tried unsuccessfully in 1957 to kill a civil rights bill.
This week, Democratic Senator Jeff Merkley delivered the eighth-longest speech, against Gorsuch, that was 15 hours, 26 minutes.
WHAT IS THE 'NUCLEAR OPTION?'?
It is Senate slang for banning filibusters through a rules change by the majority party.
In recent years, as filibusters have added to Senate gridlock, there have been threats to execute the nuclear option. Groups of senators, known as "gangs," have sometimes defused the threats.
In 2013, Democratic Senate Majority Leader Harry Reid deployed the nuclear option when he became fed up with Republican filibusters against then-President Barack Obama's nominees. He changed Senate rules to ban filibusters against the president's judicial and executive-branch nominees but left it in place for Supreme Court appointees.
Now, Senate Majority Leader Mitch McConnell, a Republican, is thought to be ready to expand the ban to Supreme Court nominees.
WILL FILIBUSTERS ON LEGISLATION BE BANNED?
McConnell has told reporters he will not broaden the ban on filibusters to legislation and does not believe Republican senators would want to do that.
Some political scientists think Democrats have more to gain than Republicans by ending filibusters on legislation.
"My sense has always been that Democratic policy priorities have suffered more from the filibuster than Republican priorities," said George Washington University political science professor Sarah Binder. That is because Democrats are more likely than Republicans to back an expansion of government programs, which generally requires legislation.
But Binder said she could imagine Democrats or Republicans trying to score a major win on an issue central to their constituencies.
For Democrats: No filibuster could mean trying to pass another major healthcare or campaign finance reform or new gun controls. For Republicans: Some sort of major deregulation of an industry or changes to "entitlement" programs such as Social Security, Medicare or Medicaid.
(Reporting by Richard Cowan; Editing by Caren Bohan and Peter Cooney)