(WASHINGTON) — When the Senate returns to Washington next week, lawmakers will be in a race against the clock to navigate a precarious political landscape in time to progress President Joe Biden’s infrastructure agenda before the summer comes to a close.

There are only four weeks remaining for lawmakers to make major moves on infrastructure, and Senate Majority Leader Chuck Schumer has promised that both a bipartisan package focused on core infrastructure items and a second, larger, fast-tracked budget bill aimed at other priorities in Biden’s American Families Plan will be introduced in July.

Prospects for the $1.2 trillion bipartisan deal, forged by a group of five Senate Democrats and five Senate Republicans got a boost Tuesday from the bipartisan House Problem Solvers caucus, who gave the proposal it’s seal of approval in a statement.

“I’m thrilled to have the Caucus’s support for our bipartisan agreement to make historic investments in upgrading America’s critical infrastructure, creating jobs and expanding economic opportunities across the country without raising taxes,” said Senator Kyrsten Sinema, D-Ariz., who led Senate negotiations on the bipartisan infrastructure package.

But critically, the caucus only lent it support to the stand-alone bipartisan bill. The group did not endorse tying the bipartisan infrastructure package to a larger bill that would be passed using a fast-track budget procedure called reconciliation, as some progressive Democrats have called for.

“We support bringing this bipartisan, bicameral proposal, which is strongly supported by the White House, to the House floor as a stand-alone vote,” Problem Solvers Caucus co-Chair Rep. Brian Fitzpatrick, R-Pa., said Tuesday. “Let us vote on this package now — no strings attached. Let this bill be considered up-or-down on its own merits.”

It is not yet clear whether lawmakers will have a chance to consider the bipartisan package separate from a reconciliation package. Democratic leaders are pursuing a “two-track” approach that would move both pieces of legislation at the same time.

Biden faced considerable backlash following the announcement of the bipartisan deal last month for saying he would only consider the bipartisan package “in tandem” with the larger reconciliation package. The president had to issue a clarification to soothe Republican detractors.

Republicans have all but demanded the bipartisan bill stand alone for it to earn their backing while progressive Democrats have threatened to vote against the bipartisan deal unless they’re assured the larger package will also pass.

Legislative language is still coming together behind the scenes while the Senate is on recess.

White House press secretary Jen Psaki said during a press briefing Tuesday that the White House is in contact with congressional staff working on crafting both the bipartisan package and the legislation that would be used in a budget reconciliation process. No bill text on either package is yet available.

“There’s a lot of work that needs to happen with Congress, and we expect over the next week there to be a lot of behind the scenes bill writing negotiations discussions on Capitol Hill, long nights, lots of coffee over the course of the next several days,” Psaki said. “Given that Leader Schumer has conveyed that he would like to see both the reconciliation package and the infrastructure bill on the floor in July, and we’re in July now in terms of the president’s priorities.”

House Speaker Nancy Pelosi reaffirmed on Wednesday that she is still committed to tying the bipartisan package to a reconciliation package. It remains to be seen if those commitments will be enough to coax progressives in both the House and Senate who are reluctant to support the bipartisan deal without assurances of a reconciliation package to vote in favor of the bipartisan deal.

Democrats are working with the narrowest of margins in both chambers. In the House, there is a slim majority. In the Senate, every single Democrat, plus the tie-breaking vote of Vice President Kamala Harris, will be needed to pass a reconciliation package that will almost certainly face unanimous opposition from Senate Republicans.

Unanimity among the Senate Democratic Caucus is going to prove its own challenge, especially under such time constraints. Budget reconciliation is a time-consuming process, and Democrats as of late are on wildly different pages about the appropriate amount of money to allocate.

Budget Chairman Bernie Sanders, I-Vt., whose committee will lead the reconciliation process, has proposed as much as $6 trillion for the second package. But moderate Democrat Joe Manchin said he will only support that which can be credibly paid for.

“I want to make sure we pay for it. I do not want to add more debt on,” Manchin said on ABC News’ “This Week.” “So if that’s $1 trillion or $1.5 trillion or $2 trillion, whatever that comes out to be over a 10-year period, that’s what I would be voting for,” Manchin said.

Republican Leader Mitch McConnell conceded at a press event on Tuesday that if all Democrats are united behind a reconciliation effort, there’s little he can do to prevent them from moving forward.

That leaves the Republican leader dependent on Manchin — as well as other moderate Democrats — who he said may find the spending levels Sanders is proposing “offensive.”

McConnell said he still sees a path forward on the bipartisan infrastructure deal but promised that Senate Republicans are “going to make it hard” for Democrats to move forward on a reconciliation package.

“This is not going to be done on a bipartisan basis,” McConnell said of the larger reconciliation package. “This is going to be a hell of a fight over what this country ought to look like in the future and that’s all going to unfold here in the next few weeks.”

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