Legislation protecting special counsel Robert MuellerRobert (Bob) Swan MuellerKamala Harris says her Justice Dept would have 'no choice' but to prosecute Trump for obstruction Dem committees win new powers to investigate Trump Schiff says Intel panel will hold 'series' of hearings on Mueller report MORE was blocked on Wednesday for a second time in the past month.

Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeJeff Flake becoming Harvard fellow Democrats needle GOP on standing up to Trump Amash gets standing ovation at first town hall after calling for Trump's impeachment MORE (R-Ariz.), joined by Sens. Christopher CoonsChristopher (Chris) Andrew CoonsDemocrats want White House hopefuls to cool it on Biden attacks Senators revive effort to create McCain human rights commission Senate Dem to reintroduce bill with new name after 'My Little Pony' confusion MORE (D-Del.) and Cory BookerCory Anthony BookerBiden to debate for first time as front-runner Rules for first Democratic primary debates announced Press: Democrats form circular firing squad 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 TrumpNew EPA rule would expand Trump officials' powers to reject FOIA requests Democratic senator introduces bill to ban gun silencers Democrats: Ex-Commerce aide said Ross asked him to examine adding census citizenship question 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 LeeOvernight Defense: Officials brief Congress after Iran shoots down drone | Lawmakers fear 'grave situation' | Trump warns Iran | Senate votes to block Saudi arms sales | Bombshell confession at Navy SEAL's murder trial The 7 GOP senators who voted to block all or part of Trump's Saudi arms sale Senate votes to block Trump's Saudi arms sale 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 CornynDemocrats give Trump trade chief high marks GOP senators divided over approach to election security GOP lawmakers want Mulvaney sidelined in budget 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 McConnellEXCLUSIVE: Trump on reparations: 'I don't see it happening' Overnight Health Care — Sponsored by Campaign for Tobacco-Free Kids — Trump issues order to bring transparency to health care prices | Fight over billions in ObamaCare payments heads to Supreme Court Hillicon Valley: Senate bill would force companies to disclose value of user data | Waters to hold hearing on Facebook cryptocurrency | GOP divided on election security bills | US tracking Russian, Iranian social media campaigns 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 ManafortREAD: Hannity, Manafort messages released by judge Manafort, Hannity talk Trump, Mueller in previously undisclosed messages FBI, warned early and often that Manafort file might be fake, used it anyway 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 SessionsTrump: Appointing Sessions was my biggest mistake Nikki Haley blasts Roy Moore's Senate bid: 'He does not represent our Republican Party' Time magazine: Trump threatened reporter with prison time 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 RosensteinTrump: Appointing Sessions was my biggest mistake Trump blasts Mueller, decries 'witch hunt' at 2020 launch Trump: I didn't fire Mueller since firings 'didn't work out too well' for Nixon 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.