Legislation protecting special counsel Robert MuellerRobert Swan MuellerSasse: US should applaud choice of Mueller to lead Russia probe MORE was blocked on Wednesday for a second time in the past month.

Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeArizona gov taps McSally for McCain Senate seat The Hill's Morning Report — What a shutdown would mean for the government Corker dodges on Trump primary question MORE (R-Ariz.), joined by Sens. Christopher CoonsChristopher (Chris) Andrew CoonsSenators prepare for possibility of Christmas in Washington during a shutdown Dem senator: Trump 'seems more rattled than usual' Dem: 'Disheartening' that Republicans who 'stepped up' to defend Mueller are leaving MORE (D-Del.) and Cory BookerCory Anthony BookerKlobuchar on 2020: ‘I do think you want voices from the Midwest’ Klobuchar moves up in Iowa poll of 2020 Dems Harris announces support for White House-backed criminal justice bill 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 TrumpREAD: Transcript of James Comey's interview with House Republicans Klobuchar on 2020: ‘I do think you want voices from the Midwest’ Israel boycott fight roils Democrats in year-end spending debate 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 LeeSenate votes to end debate on criminal justice reform bill Overnight Defense: Senate bucks Trump with Yemen war vote, resolution calling crown prince 'responsible' for Khashoggi killing | House briefing on Saudi Arabia fails to move needle | Inhofe casts doubt on Space Force GOP-controlled Senate breaks with Trump on Saudi vote 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 CornynThe Hill's Morning Report — What a shutdown would mean for the government Trump, Dems dig in over shutdown GOP lawmakers distance themselves from ObamaCare ruling 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 McConnellIsrael boycott fight roils Democrats in year-end spending debate Schumer blasts GOP request for immigration 'slush fund' Trump: 'Too early to say' if shutdown will be averted 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 ManafortJudge delays Flynn sentencing after sharply criticizing former Trump aide Presidential historian: Trump's actions may be 'definition of treason' if he knew about Russian interference efforts It’s time the UK cracked down on dirty Russian money 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 SessionsPresidential historian: Trump's actions may be 'definition of treason' if he knew about Russian interference efforts Trump admin seeks to roll back Obama-era policy on school discipline: report Trump: Sessions 'should be ashamed of himself' for allowing Russia probe to proceed 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 Jay Rosenstein10 pieces of evidence against most diabolical Russian spy ever No glory in James Comey getting away with his abuse of FBI power Mueller’s real challenge 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.