The foreboding speech from McConnell, in which he alternatively lauded the merits of the 60-vote hurdle for the Senate to pass bills and warned of a dystopian Senate if Democrats remove it, came after two Senate Democrats on Monday said on-the-record that they don't support removing the protection for the Senate minority.
After getting those pledges from Sens. Joe Manchin. D-W.Va., and Kyrsten Sinema, D-Ariz., McConnell relented on his demand that Senate Majority Leader Chuck Schumer, D-N.Y., include a provision preserving the filibuster in their power-sharing agreement in the 50-50 Senate.
McConnell said that "simple arithmetic" now assures the Senate "won't tear up a central rule."
"The Senate exists to require deliberation and cooperation. James Madison said the Senate's job was to provide a complicated check ... against improper acts of legislation," McConnell said. "We ensure that laws earn enough buy-in to receive the lasting consent of the governed. We stop bad ideas, improve good ideas and keep laws from swinging wildly with every election."
But, McConnell said, "I want to discuss the precipice from which the Senate has stepped back... So let's take a look at what would happen if, in fact, the legislative filibuster was gone."
McConnell said, in what was essentially a threat, that there would be "immediate chaos, especially in this 50-50 Senate."
"Destroying the filibuster would drain comity and consent from this body to a degree that would be unparalleled in living memory," he said. "The Constitution requires the Senate to have a quorum to do any business. Right now, a quorum is 51 and the vice president does not count to establish a quorum. The majority cannot even produce a quorum on their own, and one could be demanded by any senator at almost any time."
McConnell said that evenly-split committees would need a quorum to do any business -- which theoretically Republicans, making up half of a committee, could withhold.
"Technically, it takes collegiality and consent for the majority to keep acting as the majority at any time they do not physically ... have a majority," McConnell added. "Every Senate Democrat and the vice president could essentially just block out the next two years on their calendar. They'd have to be here all the time."
McConnell warned that in a "scorched-earth, post-nuclear Senate," Republicans could block unanimous consent requests to schedule speeches or convene before 12 p.m. McConnell added that Republicans could force all confirmations at "even the lowest level," to move at "a snail's pace."
Things would happen either "in the hardest possible way or not at all," without the filibuster, McConnell warned, and that if Democrats get rid of the filibuster "it would immediately and painfully clear to the Democratic majority that they had indeed just broken the Senate."
"It would hamstring the Biden presidency over a power grab which the president has spent decades warning against," McConnell said.
McConnell's comments came immediately after Schumer had bragged of "notable progress" on a power-sharing agreement between the two leaders after McConnell "finally relented" on "his demand for additional provisions" to the 2001 power-sharing agreement which "last governed a 50-50 Senate."
Schumer said that he is "glad we're finally able to get the Senate up and running. My only regret is that it took so long."
The agreement between Schumer and McConnell, assuming it finally materializes, would likely make Democrats the chairs of committees but allow a half-and-half split between the parties on each committee. Meanwhile, it likely would allow legislation to move to the Senate floor even if it receives a tied vote in committee.
It would also govern other rules on how the Senate will function for the next two years -- which the Senate was largely limited without. Therefore, senators started the Biden term considering his less controversial Cabinet nominees, especially on national security issues.
Now, with an agreement on how to run the chamber impending, it will be able to more capably tackle more controversial issues. The Senate will have to act quickly on immediate priorities -- the impeachment trial for former President Donald Trump starts in earnest on Feb. 9 and will take up the Senate's entire schedule until it comes to a resolution.
But, McConnell said, any progress on anything would be destroyed if Democrats get rid of the filibuster.
"Taking that plunge would not be some progressive dream. It would be a nightmare," he said. "I guarantee it."