The Senate failed to reach the 60 votes necessary to advance a bill creating a bipartisan commission to investigate the Jan. 6 Capitol riots, voting 54-35 as Republicans invoked the first legislative filibuster of the Biden presidency.

Why it matters: Democrats argue the commission is urgently needed to investigate one of the darkest days in U.S. history. Republicans fear the commission could be weaponized to damage them politically ahead of the 2022 midterms.

Zoom in: The six Republicans who voted in favor of the commission were Sens. Bill Cassidy (La.), Susan Collins (Maine), Lisa Murkowski (Alaska), Rob Portman (R-Ohio), Mitt Romney (Utah), and Ben Sasse (Neb.).

What they're saying: "I am sorry if an independent commission to study an attack on our democracy isn't a Republican ad-makers idea of a good time. This is too important," Senate Majority Leader Chuck Schumer (D-N.Y.) said on the Senate floor on Thursday.

• Schumer asked Republicans in a speech on Friday, moments before the vote: "What are you afraid of, the truth? Are you afraid that Donald Trump’s Big Lie will be dispelled?"
• "The Department of Justice is deep into a massive criminal investigation," Senate Minority Leader Mitch McConnell (R-Ky.) countered. "I do not believe the additional, extraneous 'commission' that Democratic leaders want would uncover crucial new facts or promote healing. Frankly, I do not believe it is even designed to."

Behind the scenes: Republicans have privately said that a 9/11-style commission would be a political mess for the GOP and could jeopardize Senate seats next year, Axios' Alayna Treene reports.

• Former President Trump, who remains the most popular figure in the GOP, has condemned the proposed commission as "partisan" and demanded investigations into left-wing political violence during racial-justice protests last year.
• Ahead of the vote, the mother of fallen Capitol Police officer Brian Sicknick met privately with Republicans to urge them to vote for the bill. Sen. Ron Johnson, a Wisconsin Republican who has sought to downplay the severity of the Capitol attack, said he "respectfully disagreed" with her on the "added value of the proposed commission."

Catch up quick: 35 Republicans supported the bill passed in the House, which was negotiated between the top Democrat and Republican on the Homeland Security Committee.

• Murkowski, Romney and Collins were the only GOP senators to publicly say they would vote for the commission prior to Friday — though Collins said she wanted to see changes to the House bill.
• Murkowski blasted McConnell on Friday for refusing to back the commission, accusing the leader of her party of putting "short-term political gain" over finding out the truth about the deadly insurrection.
• Cassidy said in a statement after voting in favor of advancing the bill: "The investigations will happen with or without Republicans. To ensure the investigations are fair, impartial, and focused on the facts, Republicans need to be involved."
• Moderate Democratic Sens. Joe Manchin (W.Va.) and Kyrsten Sinema (Ariz.) — who publicly oppose eliminating the filibuster — had pushed Senate Republicans to "find a path forward" on the commission so "our nation never has to endure an attack at the hands of our countrymen again."
• Manchin said on Thursday that he would not be willing to "destroy our government" by getting rid of the filibuster if Republicans blocked the commission, but added: "You have to have faith there's ten good people."

What to watch: House Majority Whip Steny Hoyer (D-Md.) previously told reporters that Democrats would likely pursue a select committee if the bill fell short in the Senate.