What is the filibuster in US politics?

Some bills with the support of fewer than 60 senators are subject to the Senate’s famous proceedings

The Senate has a long-standing practice of allowing any one senator to object to proceedings and filibuster a bill to halt action or votes. Getty Images / AFP

US President Donald Trump on Friday called on Republicans in the Senate to terminate the filibuster, a mechanism that allows politicians to block legislation.

"The Democrats will terminate the filibuster in the first hour, if and when they assume 'control' or power. Republicans have what the Democrats want – We should do it, now, and have the greatest three years in history", he wrote in a Truth Social post from a day earlier.

In a video posted a day earlier, Mr Trump called congressional Democrats "crazed lunatics" and urged Republicans to "get rid of the filibuster and get rid of it now".

But Republican majority leader John Thune threw cold water on that idea.

"I know where the math is on this issue in the Senate, and ... it's just not happening," he said.

The US Capitol building in Washington. AFP

In the US Senate, legislation usually requires the support of 60 out of 100 senators to pass. That is because under Senate rules, 60 votes are needed to stop a debate and force a vote.

Any bill with the support of fewer than 60 senators is subject to the Senate’s famous filibuster proceedings, where a senator opposed to a bill can stall it until there is no more time left for it to pass.

While Republicans hold the majority in both houses of Congress, a lengthy government shutdown has Mr Trump calling for the "nuclear option".

This is how the Senate filibuster works.

What is a filibuster?

The Senate has a long-standing practice of allowing any senator to object to proceedings and filibuster a bill to halt action or votes.

Senators have famously stood at their desks for hours making their case, as Strom Thurmond, a South Carolina senator, did to stall the 1957 Civil Rights Act.

Today, senators can merely signal their intent to object, even privately, and that is enough for Senate leaders to take action.

Leaders sometimes simply drop the issue from floor consideration. At other times, they push ahead, taking cumbersome steps to cut off the filibuster and move forward with proceedings.

What is the problem?

As the US, and Congress, has grown more partisan, the filibuster has become a key weapon in what is often described as a procedural arms race in the Senate.

Year after year, more and more senators threaten to use filibusters to block legislation. Overcoming filibusters can take days, if not weeks.

Even without a senator holding the floor, filibusters have forced them into all-night and weekend votes to advance legislation, as happened during the passage of Barack Obama’s Affordable Care Act.

Can the Senate change the filibuster?

It takes 51 votes to change the Senate rules – a tall order at most times and especially now in the evenly split chamber.

But senators have changed the filibuster rules before.

Frustrated with Republicans blocking Mr Obama's executive and judicial branch nominations, Democrats, led by senator Harry Reid of Nevada, changed the rules to set a simple 51-vote threshold for confirming people in those positions.

During former president Joe Biden's administration, several Democrats and advocacy groups called for ridding the Senate of the filibuster on legislation, but similarly, there was not enough support among Democratic senators to do so.