McConnell didn’t explain why he had decided to block the legislation. Hours earlier, however, he told reporters that he believed that special counsel Robert Mueller should be able to finish his investigation without obstructions and that he didn't believe Mueller was in danger of being fired, The Hill reported.
"There's been no indication… that Mueller investigation will not be allowed to finish, and it should be allowed to finish. We know how the president feels about the Mueller investigation, but he's never said he wants to shut it down," McConnell told reporters at a news conference.
Flake told reporters that he is concerned by President Donald Trump’s rhetoric on the Mueller probe investigating Russia’s alleged collusion in the 2016 Presidential election. Russia and Trump have repeatedly denied the allegations.
“With the firing of the attorney general… the president now has this investigation in his sights, and we all know it,” Flake said from the Senate floor, adding that “presidents do not get to determine what gets investigated and what and who does not.”
The legislation was backed by Democrats and some Republicans after Trump fired Attorney General Jeff Sessions last week and replaced him with Acting Attorney General Matthew Whitaker, Sessions' former chief of staff at the Department of Justice (DOJ).
Flake said earlier on Wednesday that he believed Whitaker shouldn’t oversee the Mueller investigation. For Whitaker “to have oversight over the investigation, that's what seems unconstitutional,” Flake said.
Flake warned on Wednesday that he and Senator Chris Coons (D-DE) will return to the Senate floor in an attempt to get the bill a vote and that he will oppose any judicial nominations until it does.
“I can't think of values held more dear than the independence of our judicial system and an electoral system free of malign influence, either foreign or domestic. When I think of the things that we hold most dear, those things are at the top of the list. It is our sworn oath to keep it that way,” Flake said.