Legislation protecting special counsel Robert MuellerRobert (Bob) Swan MuellerSchiff: Trump acquittal in Senate trial would not signal a 'failure' Jeffries blasts Trump for attack on Thunberg at impeachment hearing Live coverage: House Judiciary to vote on impeachment after surprise delay MORE was blocked on Wednesday for a second time in the past month.

Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeThe Hill's 12:30 Report: House managers to begin opening arguments on day two Flake: Republicans don't speak out against Trump 'because they want to keep their jobs' GOP senator calls CNN reporter a 'liberal hack' when asked about Parnas materials MORE (R-Ariz.), joined by Sens. Christopher CoonsChristopher (Chris) Andrew CoonsDemocrats rally in support of bill to repeal Trump travel ban This week: Senate barrels toward showdown on impeachment witnesses GOP-Biden feud looms over impeachment trial MORE (D-Del.) and Cory BookerCory Anthony BookerSenate Dems to Pompeo: Comments about NPR reporter 'insulting and contemptuous' Black caucus in Nevada: 'Notion that Biden has all of black vote is not true' The Hill's 12:30 Report: House managers to begin opening arguments on day two MORE (D-N.J.), tried to get consent to schedule the long-stalled legislation for a vote. 

Flake questioned why his colleagues weren't "up in arms" after a string of tweets from President TrumpDonald John TrumpWarren: Dershowitz presentation 'nonsensical,' 'could not follow it' Bolton told Barr he was concerned Trump did favors for autocrats: report Dershowitz: Bolton allegations would not constitute impeachable offense MORE bashing Mueller's investigation into Russian interference in the 2016 presidential election.

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"With the president tweeting on a regular basis, a daily basis, that the special counsel is conflicted, that he is leading so-called 12 angry Democrats and demeaning and ridiculing him in every way, to be so sanguine about the chances of him being fired is folly for us," Flake said.

Trump in a tweet hours before Flake's request blasted Mueller's probe into Russian election interference and possible collusion between the president's campaign and Moscow as the "angry Mueller gang of Dems" and exclaimed that it is "our Joseph McCarthy era."

But GOP Sen. Mike LeeMichael (Mike) Shumway LeeThe self-fulfilling Iran prophecy No patriotic poll bump for Trump, but Soleimani strike may still help him politically Senators are politicians, not jurors — they should act like it MORE (Utah) objected to voting on the legislation, arguing the bill had constitutional issues.

"As Justice Scalia explains, we cannot convert an office like this one ... without creating a de facto fourth branch of government fundamentally undermining the principles of the separation of powers that is so core to our liberty," Lee said.

Flake pledged that they would come back to the Senate floor to try to set up the bill for a vote again.

Under the upper chamber's rules, senators can go to the floor to request a vote or passage of any bill or nomination. But any one senator can block their requests. 

The floor drama comes after Senate Majority Whip John CornynJohn CornynBolton sparks internal GOP fight over witnesses Trump legal team begins second day of arguments under Bolton furor Trump legal team offers brisk opening defense of president MORE (R-Texas) said Republican leadership was measuring support for the bill to try resolve a standoff with Flake, who is voting against judicial nominees until the Mueller protection bill gets a vote. 

"We're whipping that to see where people are. I think the leader needs that information to decide how to manage all the competing demands on our time," Cornyn said when asked about discussions within the Republican caucus about the legislation.

But there is still fierce opposition to the bill within the GOP caucus, and Senate Majority Leader Mitch McConnellAddison (Mitch) Mitchell McConnellRepublicans show little enthusiasm for impeachment witness swap Overnight Health Care — Presented by Philip Morris International — CDC, State Department warn against travel to China | Biden says Trump left US unprepared for epidemic | Justices allow Trump 'public charge' rule to move forward Progressive group targeting vulnerable GOP senators on impeachment witnesses MORE (R-Ky.) called it a “solution in search of a problem” on Tuesday. 

The president has stepped up his Twitter attacks on Mueller's probe in recent days amid several new revelations, including the special counsel's charge that former Trump campaign chairman Paul ManafortPaul John ManafortDOJ releases new tranche of Mueller witness documents Treasury adviser pleads guilty to making unauthorized disclosures in case involving Manafort DOJ argues Democrats no longer need Mueller documents after impeachment vote MORE had violated his plea agreement. 

New reports emerged on Tuesday that Manafort's attorney had been sharing information with attorneys for Trump on his former campaign aide's cooperation with the Mueller probe. 

Trump after the midterm elections forced Attorney General Jeff SessionsJefferson (Jeff) Beauregard SessionsLawmaker wants Chinese news outlet to register as foreign agent Trump-aligned group launches ad campaign hitting Doug Jones on impeachment ICE subpoenas Denver law enforcement: report MORE to resign and named Matthew Whitaker, Sessions's chief of staff, as acting attorney general. Whitaker, who has criticized the Mueller probe, is now overseeing it in place of Deputy Attorney General Rod RosensteinRod RosensteinRosenstein says he authorized release of Strzok-Page texts Journalist alleging Obama administration spied on her seeks to reopen case Rosenstein on his time in Trump administration: 'We got all the big issues right' MORE

The Senate Judiciary Committee passed legislation that would protect Mueller, or any other special counsel, in the event he is fired, but the bill has stalled amid opposition from GOP leadership.

The bill would codify Justice Department regulations that say only a senior department official could fire Mueller or another special counsel.

It would give a special counsel an "expedited review" of their firing. If a court determines that it wasn't for "good cause," the special counsel would be reinstated.

Updated at 12:59 p.m.