President Joe Biden would not outright say on Thursday whether he supports ending the legislative filibuster in the United States Senate as progressive activists demand Senate Democrats take drastic action to pass Biden's agenda.

Biden held his first press conference as president, fielding questions from reporters on various topics. Asked to address how many votes should be required to break a filibuster — the Senate rules currently require 60 votes to close debate on an issue — Biden said he wasn't sure how many votes it would take to change the Senate's rules.

"If we could end it with 51, we would have no problem," Biden told reporters, noting that "it's going to be hard to get a parliamentary ruling that allows 50 votes to end the filibuster, the existence of a filibuster."

"But it's not my expertise in what the parliamentary rules and how to get there are," Biden added, an incredible claim from a man who spent nearly 40 years as a Democratic senator from Delaware before becoming vice president and subsequently president of the United States.

Most Democrats in recent weeks have intensified their campaign to end the legislative filibuster, citing inevitable Republican obstruction of major parts of President Biden's agenda and even resorting to claims that the filibuster, in the words of Sen. Elizabeth Warren (D-Mass.), "has deep roots in racism, and it should not be permitted to serve that function, or to create a veto for the minority."

Progressives have claimed the filibuster — a Senate rule that simply permits senators to keep debating a question (legislation, nominations, etc.) considered on the floor for as long as they are able to speak — is a relic of the Jim Crow era and a tool white supremacists used to block civil rights legislation. In advancing these arguments, Democrats often neglect to mention how frequently they filibustered legislation under President Donald Trump and other Republican presidents. Now that a Democratic president is in office and Republicans are using the filibuster to stall legislation, many Democratic senators have reversed their previously held positions on it.

Biden said the Democrats' "preoccupation with the filibuster is totally legitimate," but assured reporters the slim Democratic majority in the 50-50 Senate, where Vice President Kamala Harris holds a tie-breaking vote, will continue to advance progressive priorities "while we're talking about what we're going to do about the filibuster."

He also for the first time stated his preference for having the Senate return to a "talking" filibuster.

"I strongly support moving in that direction," Biden said.

As a United States Senator, Biden was a fierce advocate for the filibuster. In a 2005 speech, Biden said ending the filibuster, "would eviscerate the Senate and turn it into the House of Representatives."

"It is not only a bad idea, it upsets the constitutional design and it disservices the country," Biden said. "No longer would the Senate be that 'different kind of legislative body' that the Founders intended. No longer would the Senate be the 'saucer' to cool the passions of the immediate majority."

He added that, "the Senate ought not act rashly by changing its rules to satisfy a strong-willed majority acting in the heat of the moment."

What is a filibuster anyway?

The so-called Senate filibuster rule is formally known as the cloture rule — Rule 22 of Senate procedure. It's a rule that provides senators with the procedure to end debate on a question considered on the floor.

Traditionally, debate on a question in the Senate will continue for as long as each individual senator wants it to, or for so long as they are able to hold the floor and speak about the issue at hand. The senate cannot vote on the question up for debate until each senator declines to seek recognition to speak.

If no one wants to speak, the Senate must vote on the question. But as long as a senator wishes to continue debate, the senate must debate. Hypothetically, if a senator were able to talk about a bill forever, that individual senator could prevent the full Senate from moving on to a vote on the bill for as long as he could speak. That's what happens in the great movie, "Mr. Smith Goes to Washington."

An instance when a senator has recognition and refuses to yield the floor on a question is known as a filibuster.

When an enterprising "Senator Smith" is being annoying and filibustering, the cloture rule permits a three-fifths majority of senators, 60 of them, to vote to end debate on a question and move on to a vote. The cloture rule is designed to break a filibuster. The Senate twice voted to change Rule 22 and lower the 60-vote requirement to a simple majority vote — once in 2013 and again in 2017, both times for the confirmation of presidential nominees. Now Democrats want the same rules change for cloture on legislation.

It is crucial to understand that there is no actual 60-vote requirement in the Senate to advance legislation. This is a misconception. The filibuster is not a veto.

If no senator seeks recognition to speak during debate on legislation, the Senate must move on to a simple majority vote on whether to pass the bill. The reason that so many bills are filibustered and so many cloture votes are invoked in response is largely because under the current practice of the senate, filibustering requires neither time nor energy.

The current practice of the senate is that when a cloture vote fails, instead of continuing debate until every senator is no longer willing to speak, the question is tabled and the senate moves on to consider another question.

This is known as a "two-track" system, it's a practice that was adopted in the 1970s, and it's the real reason why there's a de facto 60-vote requirement for the Senate to move on to a vote on any major piece of legislation. Instead of forcing senators who want to filibuster to continue to hold the senate floor and speak for as long as they are able, the Senate agrees to put the debate aside and move on to something else.

The Senate doesn't need to change the rules

If Democrats and Republicans were serious about advancing legislation in the Senate, they can currently do so, even with a filibuster. No rule change required. They just have to enforce the other rules of the Senate that everyone likes to conveniently ignore.

Senate Rule 19 contains a provision known as the "two-speech rule." Simply, the rules state that when a senator holds the floor to speak, "no Senator shall speak more than twice upon any one question in debate on the same legislative day" without the consent of the rest of the Senate. When senators want to debate a bill, if this rule is enforced, they get two speeches during the debate. No more. Once those speeches are used up by an individual senator, that senator can no longer participate in the debate.

If the two-speech rule were enforced, then any bill that is considered by the Senate would move on to a simple majority vote as soon as every senator gave two speeches on the bill. When a senator wants to filibuster, that senator would have to be physically present on the senate floor speaking for as long as he or she is able to. When the senator is unable to speak, their speech is used up and they have one left. When everyone is finished speaking because they don't want to debate or because they are too tired to continue, the Senate votes.

Say for example the Democratic majority wanted to pass an assault weapons ban but Republicans want to filibuster. If the Democratic majority refuses to table their bill after a cloture vote fails to end debate, they can force the Republican minority to hold the floor if the GOP wants to delay a vote on that bill.

The two-speech rule would give each Republican two speeches on the assault weapons ban. If they wanted to filibuster, they would have to attempt to continue speaking for as long as possible. Filibustering would require the minority to expend time on the floor and energy speaking to delay the bill. And because it's impossible to speak forever, the filibuster would eventually end. It's not a legislative veto, it's a delay tactic to encourage debate.

Once no senator seeks recognition to speak in the hypothetical debate on an assault weapons ban, either because they don't want to speak or because they've already used up their two speeches, the Senate would take up the bill in a simple majority vote.

The proposed rules change favored by Democrats would not end a "60-vote requirement" to pass legislation. No such requirement exists. It would just make it easier for partisan majorities in the Senate to cut off debate on bills that cannot reach bipartisan consensus because they are too controversial.