Four days after a public rift imperiled President Biden’s economic agenda, congressional Democrats have embarked on the laborious process of trying to rescue it from the brink — hoping to apply their “Build Back Better” political mantra to the very spending plan that bears its name.

The task facing party lawmakers appears immense yet familiar: They once again find themselves rethinking the shape of their proposal to overhaul the country’s health care, education, climate, immigration and tax laws, trying to figure out what to slim down or scrap entirely to win the crucial support of Sen. Joe Manchin III (D-W.Va.).

The extent of Manchin’s objections became clear on Sunday, when he revealed that he would not support Democrats’ roughly $2 trillion bill as drafted, delivering what amounted to a political death blow. The statement provoked immediate outrage at the White House, which issued a rare rebuke of the moderate West Virginian that essentially accused him of having misled the president. And it put at immediate risk a soon-expiring federal child tax credit program that Democrats see as central to Biden’s legacy.

But tempers have cooled as the week has progressed. Biden said Tuesday that he still saw it possible to craft a spending deal. Senate Democrats on Tuesday night held a private call — with Manchin’s participation — to discuss their plans to resume debate and potentially vote in January. And congressional lawmakers and aides soon after resumed haggling over the finer details, believing that a compromise eventually would be within their grasp.

“I think there is overwhelming consensus that we have to find a way to get to yes,” said Sen. Chris Van Hollen (D-Md.), reflecting on Democrats’ discussions. “People are going to have to make some hard choices in order to make sure we get something big done.”

In resolving their dispute, however, Democrats also confronted the harsh reality of Manchin’s many demands. The senator has maintained that the price tag should not exceed $1.75 trillion, requiring substantial cuts beyond what Democrats had anticipated. And he has rejected the party’s original plans to lower the costs of the bill by adjusting the start and end times of its various spending programs, which he said instead should be made permanent or excluded entirely.

That left uncomfortable choices on Democrats’ horizon. Would they have to slash their plans to expand Medicare benefits to cover hearing or eliminate their proposal to invest billions in affordable housing?

Could they afford to provide seniors and people with disabilities with home-based care while at the same time pursuing the fuller spectrum of child-care spending that they would like?

And how might they seek any extension of the federal program that provides monthly payments to millions of Americans with children, given Manchin’s opposition to the idea and the spending it would entail?

“I suspect that we will ultimately get something passed in the Senate, which will be a much more narrowly focused initiative with three or four major elements that are funded more robustly,” said Rep. John Yarmuth (D-Ky.), the chairman of the House Budget Committee.

The panel this fall originally laid the groundwork for what was supposed to be a $3.5 trillion tax-and-spending measure, until Manchin sought the first round of cuts, angering Democrats at the time. Entering next year, however, Yarmuth fears the arduous process to whittle down the bill could be even harder for some to stomach.

“Can you do that and pass it in the Senate? Can you do that and pass it in the House?” he asked. “[Democrats] can’t guarantee every vote in the House if they severely weaken climate protections, if they don’t include the child tax credit. … I think there’s a real risk here.”

With the legislative process sputtering back to life, the discussions only affirmed what has been obvious to some Democrats for months: The $2 trillion bill that they once hoped to adopt by Christmas was never going to become the law of the land.

Party lawmakers had grand ambitions as part of that proposal, which builds off longtime Democratic campaign promises and economic policy blueprints unveiled by the president in spring. They hoped to expand Medicare benefits, lower the cost of prescription drugs, authorize universal prekindergarten, invest new sums to combat climate change and boost federal safety net programs. Democrats aimed to pay for the policies through taxes targeted at millionaires and companies that pay nothing annually to the federal government.

The total package came to more than $2 trillion — far less than Democrats initially sought but more than the early deal Biden had worked out with moderate lawmakers to break a months-long logjam in the fall. House Democrats adopted it in November, even as early signs emerged that Manchin did not support its contents, including its plan to provide paid family and medical leave to millions of Americans.

The crescendo finally arrived this past weekend: Appearing on “Fox News Sunday,” Manchin said he “cannot vote” to proceed with the bill, citing the fact that it could add to the deficit and contribute to a recent uptick in consumer prices. That, in turn, infuriated the White House, where press secretary Jen Psaki issued a lengthy rebuttal, noting that the measure would be financed in full and that Manchin had claimed to keep working with Democrats on a deal.

On Capitol Hill, meanwhile, party lawmakers grew enraged, feeling as if they had been misled for months. One moderate House Democrat, who spoke on the condition of anonymity this week to describe past meetings with Manchin, said they were shocked by the senator’s opposition after he repeatedly gave the impression that he would seek a compromise. That included on the issue of the child tax credit, according to the lawmaker, who added that the White House had also reassured House members that Manchin was on board with extending it.

But Democrats’ initial blinding rage began to subside by Tuesday, as they all returned to work on a bill that may determine the fate of their majority in the next election.

Speaking to reporters Tuesday, Biden tried to project a renewed sense of optimism. “Senator Manchin and I are going to get something done,” he said after sharing the full details of his response to the fast-encroaching omicron wave of the coronavirus. The White House did not respond to a request for comment.

Senate Democrats gathered on their own late Tuesday for a roughly 90-minute virtual meeting, where Majority Leader Charles E. Schumer (N.Y.) stressed that they would not give up on adopting the Build Back Better Act, according to a Democratic source familiar with the matter who spoke on the condition of anonymity to describe the private conversation. He reiterated his plans to hold a vote on the bill in January, whether it is ready or not.

Some lawmakers soon after voiced their support for Schumer’s plans to hold a vote, even though others in the party maintain personal reservations about the optics of a failed outcome on the Senate floor.

“It doesn’t just put those of us on the record who will support it, but it also makes it very clear, you know, we’re where we stand and gives us the chance to once again talk about what the substance is we’re voting on,” said Sen. Robert P. Casey Jr. (D-Pa.). “But also make it very clear that Republicans are unanimous against it. And if we have 49 Democrats or 48, whatever the number ends up being, that provides real clarity.”

Manchin, for his part, repeated at the private meeting concerns that trillions of dollars in new spending could worsen inflation, add to the debt and, in the process, imperil the country’s ability to respond to global threats, according to two other Democratic sources, who similarly spoke on the condition of anonymity. His office declined to comment.

Some Democrats also have publicly stressed their support for seeking a deal, even as they lament the cuts this might entail. Few have seen the proposal that Manchin submitted to Biden during negotiations last week, but the mere prospect that it could include money in response to climate change prompted Sen. Edward J. Markey (D-Mass.) to acknowledge it this week as a “path forward” that has “got the pieces for a deal.”

Sen. Ron Wyden (D-Ore.), the leader of the Finance Committee, in recent days released his own early blueprint for how that might look — with a focus potentially on just the policies that target drug pricing, health care and climate change. He said the cuts are “extremely disappointing,” yet perhaps politically unavoidable, given “Republican obstruction and the constraints of legislating in a 50-50 Senate.”

But whittling down the bill threatened to create even more political headaches for Democrats, many of whom already had to stomach uncomfortable cuts to slim down a measure once set at $3.5 trillion. That included a plan to provide a more ample expansion of Medicare to include dental and vision, for example, and an effort to offer free community college to Americans in need — all priorities jettisoned to address Manchin’s cost concerns.

In a sign of the tough fight to come, many Democrats have refused to budge on the future of the child tax credit in particular. Democrats had hoped to make an extension permanent as part of the Build Back Better Act, then shelved the idea in favor of a one-year addition they believed Manchin had supported. Although many Democrats say it is critical for reducing child poverty, Manchin signaled as recently as this week that he has no interest in continuing it and would instead prefer to return it to its former state with much narrower eligibility.

“We’ve been way far apart philosophically,” he said in a Monday interview with WV MetroNews radio, adding: “If it’s called a tax credit, you got to have a W-2 to where you show that you worked.”

Privately, Democrats have discussed ways they might tinker with the program to win Manchin’s vote, perhaps by capping it to those with lower incomes. But it remained to be seen whether Manchin would be open to such a deal and how firm he might hold on to his requirement that all spending in the proposal be made permanent. Such a move to extend the child tax credit could cost well over $1 trillion, making it impossible for Democrats to do much else.

On Wednesday, liberal-leaning lawmakers in the Congressional Progressive Caucus drew their own political line in the sand. Citing the importance of the president’s agenda, particularly as the coronavirus poses fresh financial threats to families, they said they would accept “no less than the elements contained in the framework negotiated by the president” this fall.

That $1.75 trillion blueprint excluded the paid family and medical leave policy, which Manchin had opposed. But it did include a one-year extension of the child tax credit set to expire at the end of December. The bloc, led by Rep. Pramila Jayapal (D-Wash.), urged Biden in the meantime to explore ways to address the rest of his agenda through executive action.

“We have worked too long and too hard to give up now, and we have no intention of doing so,” the caucus said in a statement.