The Senate is bracing for a days-long infrastructure slog that is expected to spill into early next week, after hopes of getting a quick deal unraveled. 

Senators, under the chamber’s schedule, should be starting their weeks-long August recess, leaving town until mid-September. Instead, they’ll return Saturday for the start of a lengthy, two-part infrastructure fight. 

Unless all 100 senators agree to speed up the process, the debate could keep the Senate in session well into next week as it tries to pass a roughly $1 trillion bipartisan infrastructure bill, and as Democrats seek to pass a $3.5 trillion budget resolution. 

“I am planning on being here through Wednesday,” said Sen. John Kennedy (R-La.), while adding “never estimate” summer jet fumes. 

Tempers flared late Thursday night as leadership tried to set up a marathon of votes on anywhere between 16 to 25 potential changes to the bill, followed by a vote to pass the bipartisan legislation and send it to the House.

It proved impossible to get all senators to agree to a process, a setback that left some supporters of the bill visibly frustrated. 

To get the infrastructure bill back on track, Senate Majority Leader Charles Schumer (D-N.Y.) has teed up a vote for 1 p.m. on Saturday to start winding down debate. In order to get over the hurdle, he’ll need 60 votes. 

Seventeen Republicans have helped advance the deal so far; Sen. Mike Rounds (R-S.D.), who missed the earlier votes, is also supportive. If every Democrat votes to start ending debate on Saturday, supporters will need at least 10 Republicans to end debate. 

Sen. John Thune (S.D.), the No. 2 Republican senator, predicted that the infrastructure bill, which he has voted against so far, ultimately will overcome the procedural hurdle and pass. 

“I am still operating under the assumption that there are the votes to pass it. I just think it’s now a question of timing,” Thune told The Hill. 

None of the 18 Republicans have said they would vote "no" during Saturday’s key vote. But some are viewed as potential flips and others, including GOP Leader Mitch McConnell (Ky.), couched their support, suggesting they are not locked into a position.

McConnell also warned before the amendment meltdown that Republicans still wanted more votes, telling reporters: “We still have amendments that need to be processed. Once they are, we'll be able to wind things down.” 

Leadership aides said that a subset of potential changes to the bill could still get a vote because they are relevant to the roughly $1 trillion bipartisan bill. That, according to Thune, would include two battling amendments on a crypto-currency tax that has pitted the White House against Senate Finance Committee Chairman Ron Wyden (D-Ore.). 

Senate aides separately on Friday indicated that behind-the-scenes talks are taking place that could lead to votes on additional amendments. For example, Sens. John Cornyn (R-Texas) and Alex Padilla (D-Calif.) are pressing for a vote on an amendment that would allow states to use some unspent COVID-19 relief funds on infrastructure projects. 

Failing to get 60 votes on Saturday would throw the Senate and a key piece of Biden’s agenda into chaos. If the infrastructure bill can overcome Saturday’s hurdle, however, it’s largely on a glide path to final Senate passage.

It might take the legislative equivalent of the scenic route, however. 

Under the Senate’s rulebook, opponents could require the chamber to run the clock for up to 60 hours before they can take a final vote. If they drag out all that time, that could delay passage of the bipartisan deal until early Tuesday morning. 

Republicans expect some members of their conference will want to eat up all the time, unless they have a change of heart after Saturday’s hurdle. 

“I think that they’ll insist that we use up all the debate,” said Sen. Roy Blunt (R-Mo.), a member of leadership. 

Thune acknowledged that there are Senate Republicans “who want to use it all.” 

“There will be a point at which everything becomes more clear. ... And then we’ll see from there kind of what people’s appetite is to stay on the bill,” Thune said. “I think giving everybody a day off, or a day to just regroup and everybody to dial it down a little bit is probably a good thing.”

Part of why senators were hoping to speed up consideration of the bipartisan deal — beyond the pull of the annual August recess — is that they also have to tackle a lengthy debate over Democrats’ budget resolution. 

Democrats are able to pass the budget resolution, which paves the way for their $3.5 trillion spending plan later this year, without GOP support as long as all 50 of their members stay unified. 

But to get to their endgame, they first face up to 50 hours of debate and a marathon session known as vote-a-rama, where any senator can force a vote on anything they want. The sessions, which typically run through the night and into the morning hours, make prime fodder for the sort of political messaging votes that both parties hope to use against each other heading into the 2022 midterms. 

“We will defeat all of the poison pill amendments,” Senate Budget Committee Chairman Bernie Sanders (I-Vt.) told reporters about the Democratic strategy, vowing to pass the “most consequential piece of legislation” in recent history. 

Republicans are predicting a lengthy, painful process that could match Senate records for the number of votes cast in previous, similar marathon sessions.

Cornyn indicated that he expected roughly 40 amendment votes. Votes in the Senate, which can move at a crawl, can take roughly 30 minutes if not substantially longer.

“I think there will be a pretty good appetite for a lot of votes, but hopefully we won’t start at six o’clock at night,” he said. 

Kennedy predicted that there would “be enough amendments on vote-a-rama to trigger your gag reflex.”