The next 24 hours will make clear whether Democrats are on the verge of pushing through a once-in-a-generation expansion of the social safety net or nearing a complete collapse of Joe Biden’s ambitious domestic agenda.

The stakes are as high as ever as Democrats barrel toward a make-or-break vote on a $1tn public works measure, with almost no margin for error and little time left to break an impasse that threatens to imperil the its passage – and possibly the entirety of the president’s agenda.

Assurances of progress offered little comfort to nervous Democrats on Capitol Hill, where a series of legislative and fiscal deadlines loom.

“We’re obviously at a precarious and important time in these discussions,” White House press secretary Jen Psaki told reporters on Wednesday, as Biden spent the day locked in negotiations with Democratic leadership and lawmakers.

Returning from an Oval Office meeting with Biden on Wednesday afternoon, House speaker Nancy Pelosi told reporters on Capitol Hill that she was prepared to move ahead with a vote on Thursday.

“That’s the plan,” she said, adding that they were taking it “one hour at a time”. The caveat reflected the fluid nature of the negotiations, hours after she left open the possibility that she could delay a Thursday vote on the infrastructure bill while the president worked to secure an agreement with two centrist holdouts on his broader social policy package, seen as a must-have by progressives in the party.

At the center of the uncertainty are centrist senators Joe Manchin of West Virginia and Kyrsten Sinema of Arizona. Both have indicated that the price tag of Biden’s agenda is too high, but to the immense frustration of their colleagues, have not publicly outlined what they would be comfortable with spending. Compromise is the only way forward for Democrats, who need every vote in the Senate and nearly every vote in the House.

“While I am hopeful that common ground can be found that would result in another historic investment in our nation, I cannot – and will not – support trillions in spending or an all-or-nothing approach that ignores the brutal fiscal reality our nation faces,” Manchin said in a statement Wednesday.

His position makes it unlikely that Democrats will reach a deal by Thursday, when Pelosi wants the House to vote on the Senate-passed infrastructure bill, which would spend billions of dollars upgrading the nation’s roads, bridges and broadband.

That leaves Democratic leaders in a time-sensitive bind, partially of their own making. They initially promised progressives that they would advance the infrastructure and social policy bills in tandem. At the same time, Pelosi told centrists that she would hold a vote on the infrastructure bill to the floor this week. But with Manchin and Sinema objecting to the cost of the social spending proposal, Pelosi said she was forced to shift strategy. Now she is asking her caucus to move ahead with the infrastructure bill while Biden and the senators search for a compromise.

The social policy bill has the potential to be transformative for millions of American families. Though the details are fluid and the overall package almost certain to shrink, the proposed legislation would extend the child tax credit, establish universal pre-K education, create a federally paid family and medical leave system, in addition to an array of programs to combat climate change and transition the country toward renewable energy. The plan would be paid for by trillions of dollars in tax increases on the wealthiest Americans and corporations.

The move to decouple the groundbreaking legislation from Thursday’s infrastructure bill vote has infuriated progressives, who say they will sink the infrastructure vote if there is not an agreement on the broader package. In a sign of the deep mistrust within the party, congresswoman Pramila Jayapal of Washington, the chair of the Congressional Progressive Caucus, said she wants to see the Senate approve the package first before supporting the smaller bill.

Complicating matters further, Sinema is saying she wants to see the infrastructure bill pass without delay, even as her objections to the bill risk delaying – or completely derailing – the bill’s passage.

Pelosi said there would need to be an agreement with Biden on the “legislative language” for his social policy bill before the vote on Thursday. But Manchin quickly dispelled that notion, saying that was not the timeline he was operating under.

“It’s not possible to get a reconciliation framework” by Thursday, he told reporters.

The House did move forward on one front. In a largely party line vote on Wednesday night, the House approved legislation that would suspend the debt limit through 16 December. The bill advances to a vote the Senate, where the path to overcoming Republican obstruction remains unclear.

Additionally, the Senate is expected to vote on Thursday on a bill that would avert a government shutdown at midnight on Thursday, by funding federal agencies through 3 December.

The brinkmanship has pushed the country dangerously close to financial calamity, and yet both sides appear dug in. Republicans want to force Democrats to raise the debt ceiling on their own by using the reconciliation process to circumvent the filibuster. Senate majority leader Chuck Schumer called the position hypocritical, arguing that Republicans have a responsibility to help raise the debt limit as Democrats did on three occasions during the Trump administration.

“As default gets closer and closer to becoming a reality, our Republican colleagues will be forced to ask themselves how long they are going to keep playing political games while the economic stability of our country is at risk,” Schumer said.

Meanwhile, the White House and Democratic leaders were racing against the clock to strike a deal. With little room for error, Biden continued his personal outreach to reluctant Democrats as some members doubled down publicly in TV interviews and on Twitter. Even if a consensus is reached, the laborious task of trimming and finalizing the bills remains.

Asked whether Democrats could pull it off, Psaki told reporters to stay tuned.

“It’s like an episode of a TV show,” she said, of the high-stakes negotiations. But which show depends on what happens next.

“Maybe the West Wing if something good happens,” she said. “Maybe Veep if not.”