Though Trump wants as much wall money he can squeeze out of Congress, Capito needs to get 60 votes in the Senate, and there’s no way Democrats will go along with a major budget boost. She‘s also got to cut a deal with Sen. Jon Tester (D-Mont.), the ranking member of the panel whom Trump loathes for helping to derail Ronny Jackson’s nomination to be secretary of veterans affairs.

“We want to have a bipartisan bill. I’m very committed to border wall funding in the request of the president. I want to be supportive of that,” Capito said in an interview. “Both sides, I think, are committed to working the process. And that means compromise.”

Capito, who will be accompanied by Senate Appropriations Chairman Richard Shelby (R-Ala.), is projecting optimism about securing money for Trump’s wall.

But Republicans are privately worried they will never be able to pass a spending bill that satisfies Trump. The president is already clashing with his party on immigration — trashing a bill crafted by House GOP leadership in a free-wheeling press appearance Friday, before a spokesman walked back that criticism.

Whether Republicans can convince Trump that he’s not going to get what he wants on the wall will determine whether the congressional spending process can stay on track or a shutdown showdown is likely right before the midterm elections.

Senate Republicans are currently preparing to meet Trump’s $1.6 billion wall funding request from this spring, though the White House has since increased that request to $2.2 billion, according to Republican sources. No final decision has been made in the Senate, though the Homeland Security funding bill is expected to be released this week with committee approval set for Tuesday.

But at that rate, Trump will never get the money to finish his wall even if he wins another term as president. Trump asked for $18 billion over 10 years to begin expanding the wall this year; studies project the final cost for Trump’s barrier will be several times that amount.

“We have to have the wall,” Trump said on Friday.

Later, he tweeted: “Any Immigration Bill MUST HAVE full funding for the Wall.”

The House’s Homeland Security panel hasn’t released its bill or its border wall target number. A committee aide said the process hasn’t started in earnest yet.

And Trump faces resistance from corners of his own party as well as many Democrats on his central campaign pledge, in part because he has threatened to veto any massive omnibus spending bill that might come to his desk when the next funding deadline comes up in September.

That means Congress must pass each of the 12 individual spending bills, and in the Senate that means finding Democratic support.

For now, senators are doing much of the work themselves.

“It’s difficult talking to the [White House]. They’ll agree to something and then two weeks later someone else will come up and say: ‘Oh no, we don’t agree.’ If they can’t keep their word, I don’t have time” for it, said Senate Appropriations ranking member Patrick Leahy (D-Vt.), who hasn’t even talked to the administration about the wall.

“For us to pursue the kind of approps bills we are trying to pursue, it would have to be, at least coming out of the committee, a bipartisan agreement,” agreed Sen. Roy Blunt (R-Mo.), a GOP leader and member of the Appropriations Committee.

Most Senate Democrats supported $25 billion for border wall funding in exchange for a path to citizenship for 1.8 million young undocumented immigrants in February, but they are unlikely to agree to such a large sum anytime soon absent much broader immigration reform. And the House’s last-ditch immigration efforts have been upended by Trump’s initial comments dismissing a compromise bill written by GOP leaders, conservatives and more moderate Republicans.

Until both parties in Congress can agree on an immigration reform package, the spending process is the best place for Trump to get his wall money.

Senate Republicans could choose to simply give Trump a massive lump sum of $20 billion or more in the Appropriations Committee and force Democratic senators to vote on it — amplifying the political conflict and aligning the congressional GOP with Trump. Then either the wall would garner bipartisan support, or vulnerable Democrats would be on the record against Trump’s border wall heading into elections where 10 Senate Democrats are up for reelection in states that Trump carried in 2016.

Sen. Joe Manchin (D-W.Va.) and Tester are both up for reelection in states where Trump is exceedingly popular, and both serve on the Appropriations Committee. Manchin has been battling with Republicans over his support for a border wall, arguing he’s voted in support of it as the GOP runs ads showing him saying the opposite.

And Tester, who met privately with Capito on Wednesday about the wall, is trying to keep the appropriations bill on the rails. Tester said he thought $1.6 billion is “adequate” for funding and questioned whether the administration is prepared to even spend that amount of money.

“Whatever deal that Shelley and I come up with is a deal that would work to make this country secure. I don’t think it would be wise to blow it up,” Tester said.

Republicans acknowledge that satisfying the president will be difficult. But they also think that that getting Trump his full wall funding this year could make a dramatic difference in the midterms by boosting GOP enthusiasm and energizing the president.

“It’s something that most of our candidates would like to have. To say something we’ve done, to point to,” said Sen. John Thune of South Dakota, the No. 3 GOP Senate leader. “It’d be something that would be nice to have an accomplishment on, and it would be a good talking point for everyone that’s running.”

But given the GOP’s slim 51-seat majority, he acknowledged it would be a “heavy lift” for Republicans to provide much beyond $1.6 billion given the need for Democratic votes.

And some Republicans don’t want to give more, either. Sen. Rand Paul (R-Ky.) called spending billions upon billions on a border wall “outlandish.”

“I’m for some sort of security and barrier. But I don’t think once you’re for that that you should throw out your notions of conservative spending with taxpayer dollars,” Paul said. “I’m not for $40 billion for a wall. I just don’t think we have it.”

And that’s why the best Congress might be able to do this year is give Trump a small down payment on his wall. Republicans will start to get a sense on Monday whether it’s enough to satisfy the president.

“We’re working on that,” Shelby said. “We’ll have to see what we can do, OK?”

Elana Schor contributed to this report.