Liberals have protested the bipartisan deal's potential passage unless it is married with a spending bill running into the trillions and tackling climate change, prescription drugs, Medicare expansion and many more of the Democratic Party's progressive priorities.

Republicans were always aware that Democrats might try and pass that bigger bill using the filibuster protections of the budget. Some in the GOP even suggested the two-step process, predicting that they could more easily scuttle a Democrats-only bill if that proposal resorted to tax increases to expand social programs.

Moreover, several Republicans recently shrugged off the possibility of a two-track approach as something they have no control over. But Biden's clear vow to hold up any bipartisan infrastructure bill Congress passes until he gets the Democratic proposal done is viewed as a potential dealbreaker for these Republicans.

One aide said that clearly linking the two infrastructure bills was never discussed — not within the group of 10 senators who met Biden on Thursday, the bigger group of 21 senators who endorsed their work, or with the White House. A second aide said that frustrations run far deeper than Sen. Lindsey Graham (R-S.C.), who began griping publicly late Thursday.

"In endorsing the deal, Biden praised the group for 'keeping their word,' but then immediately broke his," said a third Republican aide.

If the Republicans were to pull their support, it would yank the rug out from under Biden after his victory lap for bipartisanship. And it would leave Democrats to come up with their own proposal. In the White House’s view, top aides and Biden had been careful for months not to appear to aggressively put one set of interests over another, for fear of alienating either the left or the right.

The Democratic majorities in Congress have been pursuing a two-track approach for several weeks. Senate Majority Leader Chuck Schumer and House Speaker Nancy Pelosi have been emphatic that the bipartisan deal offering $579 billion in new spending would never pass without being paired with the larger, Democratic-only bill.

Pelosi can withhold passage of the bipartisan infrastructure bill on her own, and has vowed to do so to make sure the Senate approves a large bill via the budget reconciliation process that can skirt a GOP filibuster. And the White House defended Biden’s consistency on Friday.

"That hasn't been a secret. He hasn't said it quietly,” said White House press secretary Jen Psaki when asked about GOP griping over Biden's comments on Thursday. "I will say that the president's view is that the public, the American people, elected him to not lead on process but to get things done. The leadership of the House and Senate are going to determine sequencing and timing."

Psaki offered “good luck” to Republicans who oppose the bipartisan plan because of the sequencing of the two bills. Republicans who would "vote against a historic investment in infrastructure ... simply because they don't like the mechanics of the process," she told reporters, are making "a pretty absurd argument."

The Republicans who met with Biden on Thursday were Sens. Rob Portman of Ohio, Susan Collins of Maine, Lisa Murkowski of Alaska, Bill Cassidy of Louisiana and Mitt Romney of Utah.

On Fox Business on Thursday evening, Cassidy seemed to throw his hands up at trying to influence how Democrats handle the process.

“I cannot control what Democrats do,” Cassidy said. “So I think we’ve made progress, even if Majority Leader Schumer decides to proceed with another reconciliation bill.”

Members of the group in each party will discuss the imbroglio on Friday afternoon, a call first reported by the Washington Post.

Senate Minority Leader Mitch McConnell (R-Ky.) signaled a strategic change on Thursday when he accused the White House of “caving completely in less than hours.” Graham’s criticism followed shortly thereafter.

In a sign of the stakes of the bipartisan agreement, Biden held a Friday call with Sen. Kyrsten Sinema (D-Ariz.), the lead Democratic negotiator. According to a readout of the call from the White House, Biden reiterated that “he would fight to pass the bipartisan agreement” and that he looked forward to signing both the bipartisan bill and the Democratic bill into law.

Natasha Korecki and Maeve Sheehey contributed to this report.

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