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 FlakePollster says Trump unlikely to face 'significant' primary challenge Trump gives nod to vulnerable GOP Sen. McSally with bill signing Flake opens up about threats against him and his family MORE (R-Ariz.), joined by Sens. Christopher CoonsChristopher (Chris) Andrew CoonsMenendez, Rubio lead Senate effort to regulate Venezuelan sanctions Dem report questions State Dept. decision to revoke award to Trump critic Senate Dem calls on Trump to apologize for attacks on McCain MORE (D-Del.) and Cory BookerCory Anthony BookerHillicon Valley: Washington preps for Mueller report | Barr to hold Thursday presser | Lawmakers dive into AI ethics | FCC chair moves to block China Mobile | Dem bill targets 'digital divide' | Microsoft denies request for facial recognition tech Booker calls for sweeping voting rights reforms 20 Dems demand no more money for ICE agents, Trump wall 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 TrumpHouse Dems demand Barr cancel 'inappropriate' press conference on Mueller report DOJ plans to release 'lightly redacted' version of Mueller report Thursday: WaPo Nadler accuses Barr of 'unprecedented steps' to 'spin' Mueller report 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 LeeDems sound alarm over top DOJ nominee Restore Pell Grant eligibility to people in prison Former Democratic aide pleads guilty to doxing GOP senators attending Kavanaugh hearing 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 Cornyn Embattled senators fill coffers ahead of 2020 Trump struggles to reshape Fed Congress opens door to fraught immigration talks 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 McConnellThe Hill's 12:30 Report: Trump, Dems prep for Mueller report's release McConnell touts Trump support, Supreme Court fights in reelection video Why Ken Cuccinelli should be Trump's choice for DHS 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 ManafortFederal judge considers setting ex-Obama counsel's trial for August: reports Juan Williams: The high price of working for Trump Ex-Obama counsel pleads not guilty to charges tied to Ukraine lobbying 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 SessionsThe problem for Trump appointees Juan Williams: The high price of working for Trump Trump learns to love acting officials 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 RosensteinHouse Dems demand Barr cancel 'inappropriate' press conference on Mueller report Mueller won't attend Barr press conference on report Schumer slams Justice Dept over 'pre-damage control' on Mueller report 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.