Updated January 20, 2022 at 12:12 AM ET

After Senate Republicans on Wednesday blocked a floor vote on two voting rights bills that President Biden has said are a moral imperative, Democrats failed to unite in a push to change Senate rules that would have sidestepped the GOP opposition, formalizing a fracture within their caucus that was looming for weeks.

The rules of the chamber require 60 votes to overcome a threatened filibuster and move forward on most legislation, meaning 10 Republicans would have to join the 50 Democratic senators to advance their voting rights bills. But all 50 Republicans stood in opposition.

Democrats then moved ahead with an effort to modify the filibuster in order to try to pass the voting rights bills with a simple majority. Senate Majority Leader Chuck Schumer, D-N.Y., proposed a "talking filibuster," which would require Republicans to talk on the floor to sustain their objection to the legislation.

"We're simply talking about restoring the Senate to what it once was, so we can have debates and we can actually vote on bills," said Sen. Amy Klobuchar, D-Minn.

But two key Democratic holdouts, Sens. Joe Manchin of West Virginia and Kyrsten Sinema of Arizona, would not support changes to the filibuster, despite dire calls in their party, arguing that democracy itself is on the line, and threats of primary challenges when the two senators are up for reelection in 2024.

In a statement after the vote, Biden said he is "profoundly disappointed that the United States Senate has failed to stand up for our democracy. I am disappointed — but I am not deterred. My Administration will never stop fighting to ensure that the heart and soul of our democracy — the right to vote — is protected at all costs."

Earlier Wednesday, Manchin reiterated his opposition to the filibuster changes in a floor speech — while Biden was giving a press conference to mark his first year in office.

Manchin warned that "the Senate will be a body without rules" if the exception to the filibuster were made for voting rights.

And Sinema said on the Senate floor last week: "While I continue to support these bills, I will not support separate actions that worsen the underlying disease of division infecting our country."

McConnell praises Sinema and Manchin

Republicans hailed their opposition, saying it preserved the integrity of the Senate by protecting the rights of the minority.

"This very day that we are just wrapping up is in all likelihood the most important day in the history of the Senate as an institution," Senate Minority Leader Mitch McConnell, R-Ky., said ahead of the vote on the filibuster. He referred to the Democratic proposal as "a plot to break the Senate."

Schumer responded: "Even for those who feel that the filibuster is a good thing and helps bring us together, I would ask this question: Isn't the protection of voting rights, the most fundamental wellspring of this democracy, more important than a rule in this chamber?"

Democrats also said that there was gravity in the moment as they argued for bills meant to combat voter restrictions Republican-led legislatures have put into place in recent months.

"This is not just another routine day in the Senate. This is a moral moment in America," said Sen. Raphael Warnock, D-Ga., who was elected last year after serving as senior pastor at Ebenezer Baptist Church in Atlanta where the Rev. Dr. Martin Luther King Jr. preached.

"Dr. King said, 'History has thrust something upon me from which I cannot turn away,' " Warnock added during Senate debate on Wednesday. "We have been summoned, all of us. We cannot turn away."

What's in the bills

The Senate had canceled a planned recess this week to debate the two bills — the Freedom to Vote Act and the John Lewis Voting Rights Advancement Act.

Senate Democrats got around a GOP filibuster to start debate on the measure, but under current rules, they still needed 60 votes to end debate and proceed to a vote.

Democrats hold a slim, technical majority in the chamber. Each party holds 50 seats, but Vice President Harris, a Democrat, would act as the tiebreaker in the event of an voting impasse. Harris presided over the Senate Wednesday night as the voting bills were blocked.

"The president and I are not going to give up on this issue," Harris told reporters after Republicans blocked the legislation. "This is fundamental to our democracy and it is non-negotiable."

The John Lewis Voting Rights Advancement Act, named for the late Georgia congressman and civil rights icon, aims to reverse a 2013 Supreme Court decision that struck down key portions of the Voting Rights Act of 1965. Specifically, it would restore a requirement that mandates states with a history of voter discrimination get preclearance before changing voting laws, and it would update the formula used to determine which states must get preclearance.

The Freedom to Vote Act is even more sweeping measure; it would, among other things, make Election Day a national holiday and expand voting by mail.

While Democrats have positioned these issues as foundational to maintaining a healthy democracy, Republicans, still reeling from their 2020 election losses, White House and Senate losses, say that recent GOP-backed laws, including limiting mail-in voting and shortening the implementing more stringent voter ID laws, are simply common sense.

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