Collectively, the engagement underscores the degree to which both the White House and its allies are worried that the administration’s request — or at least something resembling it — won’t make it through Congress quickly. And it reflects the hurdles that come with divided government, in which intense opposition among a segment of House conservatives, and a smaller subset in the Senate, can quickly complicate a top agenda item for the president.

Biden aides remain confident Congress will pass an aid bill even as they concede that the legislative process means any final version won’t exactly match their request. A White House official on Tuesday expressed openness to engaging on the border aspects of the bill, a move that would bring the administration closer to the Senate GOP’s top demand.

“I think we will get something through with all components,” is how one top White House official put it, summarizing the optimistic read of the situation.

House Speaker Mike Johnson’s (R-La.) decision, though, to muscle through an Israel-only bill that slashes key IRS funding sparked concern among lawmakers who generally believe emergency funding doesn’t need to be paid for or otherwise offsets. And centrists are worried about how Congress is going to clean up the messy politics of the moment.

“I wish that I could say that now that the House has a speaker and that they’re back in, that we’ve got some more certainty with how we’re going to move on this supplemental,” said Sen. Lisa Murkowski (R-Alaska). She also mentioned another dire concern: the Nov. 18 shutdown deadline.

“I certainly hope we are not at that point in 18 days where we haven’t figured out how to keep the government open,” Murkowski added. “And we haven’t sent a strong message from the U.S. Congress about our support for Israel, our support for Ukraine and supporting ourselves here, from the border perspective.”

But Blinken and Austin’s forceful testimony in the Senate’s first hearing on the supplemental request Tuesday — and the bipartisan support they got — temporarily assuaged some White House allies, who have been privately concerned about the funding package.

“Based on the appropriations hearing today, I am confident,” said Sen. Jon Tester (D-Mont.). “But things change.”

Administration officials are most fearful over the future of Ukraine funding. The $60 billion the White House requested for the beleaguered nation was always aspirational. But in their conversations with lawmakers, Biden administration officials have stressed the importance of keeping Israel and Ukraine aid together.

“They have made it very clear that Ukraine is just as important” as the Israel funding, said Sen. Ben Cardin (D-Md.), chair of the Senate Foreign Relations Committee.

The White House’s best-case scenario would have had Schumer and McConnell finding an aid figure that could overcome a filibuster and then daring the House to reject it. But while McConnell has supported robust Ukraine funding and pairing it with Israel aid, he has wanted to see a stronger border security component in the package — which he sees as a must-have in order to win enough GOP buy-in. It’s also not clear whether such a bill would be jammed into the continuing resolution which must pass Congress before the end of Nov. 17.

Sen. John Cornyn (R-Texas) said a group of Senate Republicans is closing in on a decision on a border policy demand that they hope to get into the package. He called the legislation “a single point of leverage” and expressed hope that there would be 41 Republican votes to block moving on any bill without border policy changes.

Biden and McConnell have decades of history in working together, which has Democrats optimistic that differences will be resolved.

“I certainly believe the president has a good relationship with him and should work with him,” said Senate Majority Whip Dick Durbin (D-Ill.).

But McConnell has his own limitations internally, including duress from conservatives for publicly breaking with Johnson over the foreign aid approach.

There are other potential issues with the White House request in its current form. In particular, some Senate Republicans are concerned with the humanitarian funding in the administration’s request, citing worries that money designed to help everyday Palestinians could end up in the pockets of Hamas. GOP senators are also signaling they’re open to trimming the Ukraine funding in Biden’s request, presumably to entice House Republicans who’d rather not pair the aid to both nations.

“There are some elements of [the package] that our members have significant heartburn with,” said Sen. John Thune (R-S.D.), who has been supportive of Ukraine funding.

White House aides did not anticipate that Johnson would merely roll over on funding once he got the gavel. But they viewed his move to tie Israel aid to IRS enforcement cuts week as a misstep. The White House official called it “a gift” that allowed them to portray Republicans as rewarding “wealthy tax cheats.”

House Democrats, likewise, have largely balked at the measure, noting that it doesn’t just claw back a key part of Democrats’ landmark bill from last year but also includes no humanitarian aid for Gaza. One Democratic member, who was granted anonymity to speak candidly, called the GOP’s bill “appalling.”

“I won’t vote for it with these cuts and I won’t vote for it without humanitarian aid,” the member said. “I might be able to be convinced to vote for it without Ukraine funding if there was a firm plan for that in the near future, but the current proposal is a huge no.”

The break between the House and Senate was on full display on Tuesday, when Blinken and Austin testified before the Senate Appropriations Committee. The two warned that pulling Ukraine funding from the package would be a win for Vladimir Putin, and that the strongman has ambitions beyond Kyiv.

Senators on both sides of the committee voiced support for linking the two conflicts, in contrast to the House’s Republican skeptics of further Ukraine funding. But that comity didn’t extend to the gallery, where activists held up red stained hands (symbolizing blood) behind Blinken, accusing him of perpetuating violence against Palestinians.

It was a vivid illustration of the rapidly shifting political landscape that is challenging the president. And another one was soon to come. Blinken, whose stepfather was the only member of his family to survive the Holocaust and who has been working for weeks to increase aid into Gaza, departed the Senate hearing and promptly crossed the Capitol to Johnson’s offices. As he left the meeting, his vague response only hinted at the challenges ahead for the administration.

“It was a very good meeting” with Johnson, Blinken said. “I really appreciate the opportunity. I’ll leave our conversation at that.”

Daniella Diaz, Holly Otterbein and Sarah Ferris contributed to this report.