Those comments prompted an immediate war with the White House, who took personal aim at Manchin for what officials saw as a breach of trust. White House press secretary Jen Psaki released an unusually blunt statement saying that Manchin's comments "are at odds with his discussions this week with the President, with White House staff, and with his own public utterances."

In announcing his opposition, Manchin raised the same concerns about the bill that he’s had all along: inflation, rising debt and a mismatch between the package’s 10-year funding and its shorter-term programs. But until Sunday, Manchin had never taken a hard line on the legislation. In the past week, he’s spoken directly to Biden several times, with the president and other Democrats furiously lobbying him to support the bill.

With an evenly split Senate, Senate Majority Leader Chuck Schumer needs every Democrat to go along with the legislation, which only requires a simple majority vote. That dynamic gives Manchin enormous leverage over Biden's agenda, allowing him to single-handedly sink a priority that Democrats have spent much of the year working on.

Manchin’s rollout on Fox News infuriated Democrats Sunday morning. Psaki said that the senator had brought Biden an outline of a bill similar in size and scope that "could lead to a compromise acceptable to all."

"If his comments on FOX and written statement indicate an end to that effort, they represent a sudden and inexplicable reversal in his position, and a breach of his commitments to the president and the senator’s colleagues in the House and Senate," Psaki said. "Just as Senator Manchin reversed his position on Build Back Better this morning, we will continue to press him to see if he will reverse his position yet again, to honor his prior commitments and be true to his word."

And while the centrist senator’s staff informed White House and Democratic aides about his forthcoming blow to Biden’s agenda, some Democrats were steamed that Manchin himself hadn’t called Biden or Schumer.

"Manchin didn't have the courage to call the White House or Democratic leadership himself ahead of time,” fumed one Democrat familiar with internal conversations.

At the same time, Biden's Thursday's statement, which name-checked Manchin and asked for more time to negotiate on the sweeping bill, irked the West Virginia Democrat. Manchin said afterward: "It's his statement, not mine."

Manchin’s clear pronouncement that he opposes the legislation is a huge setback for Democrats, who tried to separate out Biden’s agenda into two bills to pass his jobs and families plan. Now, Manchin’s bipartisan infrastructure bill is law but the party-line effort to pour money into education, health care, climate change and tax reform is dead in its current form.

Manchin had few defenders in his own party on Sunday. The only people praising him were Republicans, who have tried to get him to switch parties and hand them the majority. Manchin has refused repeatedly.

The White House’s frustration level with Manchin grew dramatically in recent days after Manchin and Biden’s telephone negotiations went nowhere. Biden has always gotten along personally with the senator and has long believed he should not push his former colleagues. Plus, White House aides were comfortable — if not delighted — with the party-line bill slipping into early 2022.

The West Wing saw Manchin's Sunday comments as a shocking about-face — White House officials believed he had been sending signals that a deal could eventually be struck. It comes as Biden ends 2021 facing a confluence of crises: Covid cases are surging throughout the nation, inflation remains high heading into the holidays, a renewed push on voting rights already seems stalled and now the signature piece of Biden’s agenda is in grave danger.

It also undermines Biden’s central political arguments to the American people: that he could make government work again, that it's possible to deliver huge, significant changes to societal norms that impact Americans of middle and lower incomes. But now, even though his own party holds all branches of government, his agenda is in jeopardy.

Manchin’s position is a validation of progressive fears — they believed passing that infrastructure bill was a mistake without an explicit guarantee from all 50 Democratic senators to support the rest of Biden’s agenda. Sen. Bernie Sanders (I-Vt.) said Sunday he “absolutely” wants to see a vote on the legislation.

“We’ve been dealing with Mr. Manchin for month after month after month,” Sanders said on CNN’s "State of the Union." “Let him vote no in front of the whole world.”

In his TV appearance, Manchin said he would be fine voting on the bill.

If the bill ever comes to the floor, it won’t be for a few weeks. The Senate left town on Saturday morning for the holidays and won’t return until early January.

That means the Democrats’ expanded child tax credit will expire at the end of this month. Manchin disliked that the credit would only be extended by a year in the House-passed spending bill, even though most Democrats assume the party will keep trying to extend it permanently.