Things are so bad that Senate Majority Leader Chuck Schumer is now openly entertaining rules changes and singling out Rubio (R-Fla.), with whom he once worked on immigration reform. Schumer's deputy, Majority Whip Dick Durbin, said Democrats should entertain rules changes not just to the filibuster’s 60-vote threshold but the humdrum rules that empower individual senators to threaten a government shutdown or debt default if Congress gets too close to a critical deadline.

“You know the vulnerability of the Senate. It only takes one … Schumer’s earning his paycheck this week,” Durbin said. He said he sometimes tells more junior senators, “If you’ve been here less than 10 years, you won’t know what the Senate is."

Sen. Mike Rounds (R-S.D.) said that Democrats’ management of the calendar allowed his GOP colleagues to seize their leverage and “that’s their right.” But his frustration with the Senate’s quagmire is palpable.

“Here we are in December, we don’t have a national defense authorization act completed. We don’t have an appropriations process completed. We’ve got a debt ceiling limit we’re going to run up against once again. And there’s only four or five items for the whole year you’re expected to get done,” Rounds said. “I’m just tired of it.”

Veteran senators said leverage-seeking by individual colleagues is becoming only more common, and things are unlikely to improve in the coming years. More conservative, rabble-rousing Republicans are favored to prevail in several GOP primaries next year. And as long as Biden is president, Republicans will seek ways to foul up his agenda through the rule book.

The current pattern intensifies the Senate’s famous flair for the dramatic; think long filibusters and marathon voting series. Lately Republicans are getting even more creative: Just this year, Wisconsin Sen. Ron Johnson forced a clerk to read all 628 pages of Democrats’ coronavirus rescue bill. And Tennessee Sen. Bill Hagerty forced a lengthy delay of Biden’s infrastructure bill and competitiveness legislation as former President Donald Trump cheered him on.

Those stunts annoyed their colleagues, but this month’s series of impasses comes with real stakes.

“It’s hard to run this place on a good day, I think there’s a general frustration that we’re not planning as well as we could,” said Sen. Lindsey Graham (R-S.C.). He added that “I don’t think anybody can be overly surprised that Sen. Lee” would be making the demands he’s laid out.

The Senate eventually accommodated Lee, because he had no hope of winning on his amendment due to GOP absences. But ahead of that solution, senators preemptively traded blame as a shutdown threat, although short-term, became more real. Schumer said a potential funding lapse would be “a Republican anti-vaccine shutdown.” Lee shot back that “Schumer is accusing us of wanting to shut down the government by helping cram through a bill” many Republicans oppose.

The Utah conservative said he merely wanted an amendment vote — albeit at a simple majority threshold rather than the usual 60-vote margin in the chamber. There was no solution to his demands as of Thursday afternoon, according to a Republican who attended the daily party meeting. But as Thursday evening grew near, everyone was ready to go home.

Though Lee and his colleagues often take rogue positions, Democrats insist Senate Minority Leader Mitch McConnell could do more to corral his members. Asked about McConnell’s disagreement with some of his members' tactics, Sen. Sherrod Brown (D-Ohio) quipped: “That was a joke, that question.”

“Mitch McConnell has done ... what, to fix this?” Brown said. “McConnell can fix this in 15 seconds.”

Still, McConnell insisted all along there would be no shutdown this week. Schumer indicated that McConnell had signed off on a package of more than 20 defense bill amendments this week, more floor votes on changes than any Pentagon policy bill has had in the last four years combined.

But Rubio is sticking to his procedural guns, saying Thursday he will not consent to holding a vote on those amendments until he has a path for his provision on Uyghur labor to become law. As a result, House and Senate leaders may need to pull the bill from the floor and finish it out behind closed doors. They may even add the debt ceiling to the mix to avoid playing with a credit default.

The Senate hasn't proven much easier to manage when Republicans were in charge. McConnell encountered a similar debacle in 2018 when Sen. Rand Paul (R-Ky.) temporarily shut down the government after being denied a vote on his amendment. And Trump refused to sign a spending bill that the Senate approved late in 2018 over border security, spiraling portions of the government into the longest shutdown ever.

With that in mind, Republicans argue Schumer should have seen the current predicament coming and allowed time for last-minute hiccups.

“When you put things off to the last minute, you empower individual senators to say ‘I don’t agree,’” said Sen. John Cornyn (R-Texas.), who is close to McConnell. “If you plan better and you anticipate these differences … This is pretty predictable and unfortunate."

Still, some view the last week in the Senate as yet another nosedive in a years-long decline in cooperation within the chamber. While this year has seen some bipartisan breakthroughs — like the $550 billion infrastructure package and legislation to compete with China — it’s ending on a bitter note with major ramifications for the military, federal workers and the broader economy.

“Our national politics have become less and less tolerant, less and less respectful, less and less constructive, and we’re a representative body,” said Sen. Chris Coons (D-Del.). “Clearly there’s a rising number of House and Senate members whose home states are saying 'go to Washington and stop those fill-in-the-blank.’”