Democrats say getting the $3.5 trillion social spending plan through the House is going to be a tough road, with Speaker Nancy Pelosi (D-Calif.) only being able to afford three defections to get the measure passed. 

While debate in the Senate has received more attention, centrists are also vocally wary of the plan in the lower chamber, while progressives aren’t interested in bending at all. 

Some are already privately urging President Biden to be even more involved in the negotiations on the package with Pelosi, arguing a showing of support for his own agenda will be crucial to getting the bill signed into law.

“We are going to need the White House to be all in,” said Rep. Pramila Jayapal (D-Wash.), who chairs the Congressional Progressive Caucus and has worked closely with the highest levels of the administration on the recent deliberations. “They have been transitioning to being that and have been extremely involved in the last couple of weeks."

Most of the public scrutiny around the massive budget plan has focused on Senate tensions, with Sen. Joe Manchin (D-W.Va.) taking a starring role by calling for a pause in work and a much smaller measure. 

“We don't know where it's going to be,” he told CNN anchor Dana Bash on Sunday. “It’s not going to be at $3.5 [trillion], I can assure you.” 

Yet the House will be equally pivotal to the passage of the package, and Democrats are now warning that the process will be tougher than some may have anticipated.

“There are plenty of Joe Manchins in the House that we have to deal with,” Jayapal told The Hill in an interview this week. 

Jayapal is in regular contact with the White House as well as Senate Majority Leader Charles Schumer (D-N.Y.) about preserving the slate of priorities put forth by the progressive caucus. 

On Monday, House Democrats released a proposal to raise taxes on corporations and the wealthy to pay for a portion of the bill’s cost, though progressives argue the proposal isn’t big enough.

Democrats acknowledge there’s little room for error. 

With a strikingly narrow majority, defections from centrists or progressives could sink the legislation. Last month, a small group of centrists sought to convince Pelosi to pass a separate infrastructure bill before the budget reconciliation package. She in turn set a deadline of Sept. 27 to vote on infrastructure, an artificial date that Manchin said on Wednesday would “be very hard to do.”

When the senator asked to press “pause” on the bill last week, Pelosi said she intended to move ahead as planned. “We’re on a good timetable, and I feel very exhilarated by it,” she told reporters. The House is not set to reconvene until early next week.

One of the most influential go-betweens for the Biden administration and Capitol Hill, House Majority Whip James Clyburn (D-S.C.), said that the way the chamber is structured presents inherent challenges to creating a streamlined process to get the bill passed. He argued that Democrats should pay closer attention to the conversations being had in the House. 

“The House is a much more difficult area to navigate than the Senate,” Clyburn told The Hill in a Monday interview.

The South Carolina kingmaker, who became a vital voice in Biden World after he helped the president resurrect his primary campaign, said he has had private talks with Biden about the substance of the legislation and pushed back against the narrative emerging among some in the party who say the president is not doing enough to help get the bill through Congress.

“I don’t know if anyone knows how active or inactive the president is on this,” Clyburn said. “When you’re in these kinds of negotiations, everything you do is not necessarily in the public arena.”

Clyburn also suggested the political pressures in the House are in some ways more potent than the Senate since each representative in the lower chamber will face voters in the midterm elections in 2022.

“Every member of the House is running next year. Only one-third of the Senate is running next year. That has its complications,” Clyburn said. “The House is much more diverse than the Senate. That has its complications. That’s not just gender-wise and ethnicity, but it’s also backgrounds and experiences.”

Some are raising questions about just how much involvement Biden can actually have in the House debate. The Democratic caucus consists mostly of progressives, some of whom are well to the left of the centrist president. It is Pelosi who knows the heartbeat of the House Democratic Caucus, though it’s also clear Biden could have an influence — particularly with wavering moderates.

“If Pelosi needs Biden, she'll call him in. Otherwise, Biden will work the Senate, and Pelosi the House,” said Robert Reich, who served as Labor secretary under former President Clinton. “They’re both political pros who together have clocked almost 80 years on the Hill.”

Some Democrats who align with Sen. Bernie Sanders’s (I-Vt.) wing of the party said they are being pleasantly surprised by the Speaker’s willingness to side with progressives in her caucus time and time again. 

The latest was during the standoff with centrists over the budget and the infrastructure bill passed by the Senate, when several moderates wanted the House to vote on the infrastructure bill before the budget.

As both camps continue to dig in, observers say Biden will have to be flexible and nimble to get the bill through the House and the Senate. 

“He is appropriately calculating that if he convinces the electorate on the merits of the legislation, it will significantly raise the odds of bringing together Democrats across the political spectrum and get the legislation successfully through the reconciliation process,” said Mark Zandi, the chief economist at Moody’s whose financial analysis is often touted by White House chief of staff Ron Klain.

“I suspect that as the legislative process gets closer to the finish line and lawmakers’ positions become clearer, he will pivot and focus on the individual requirements of Democratic senators to sign onto the legislation.”