Conservatives in the House Freedom Caucus, meanwhile, want even deeper mandatory spending cuts and a commitment that they will go toward trimming back welfare programs. With moderates already balking, however, Republican leaders are unlikely to go much further. “That number is not changing,” a senior GOP aide told me. “The choice is not between $200 billion and $500 billion. It’s between $200 billion and zero.”

Another demand from the Freedom Caucus points to a bigger potential problem for Ryan and his lieutenants—a lingering mistrust between conservatives and the leadership that was exacerbated by the contentious debate over repealing Obamacare. They want to see the tax-reform proposal before voting for the budget that would allow it to move forward. “At a minimum, we’ve got to know more than we know now,” Jordan told me in a phone interview. “Once you open up the door, you can’t close it. So you’d kind of like to know what’s on the other side before you open it.

“We tried this with health-care reform,” he continued. “The plan that we thought we were going to do was not the plan that was undertaken, and look what's happened.”

“We just don’t want some surprise popping in there,” added Representative Dave Brat, a Virginia conservative.

Jordan and other conservatives scored a victory last month when Ryan agreed, in a joint statement with Senate and White House negotiators, to set aside his push for a border-adjustment tax that would help pay for cuts to the individual and corporate rates. But Jordan is worried that GOP leaders will propose other taxes as a means of offsetting rate cuts that they don’t believe are necessary.

“All we’re saying is: Show us the bill,” he said.

Right now, the bill doesn’t exist. Negotiators released only a five-paragraph statement of principles before the congressional recess and are working on writing legislative language this month. But while the White House wants the House to begin marking up a bill right after Labor Day, there is little expectation it’ll be ready that quickly, and leaders on the House Ways and Means Committee have notably set no timetable for finishing their work beyond saying it’ll get done this year. Another option for House leaders is to abandon the full budget altogether and do what they did on health care: pass a stripped-down “shell” budget that merely contains instructions for tax reform and sets aside other policy issues. “Everyone wants to get a real budget. We're not entertaining that option yet,” a senior GOP aide told me.

The irony is that among Republicans, conservatives are the most invested in the reconciliation process that they are, for the time being, holding up. GOP leaders could skip right to tax reform without a budget, but then they’d need 60 votes in the Senate and Democratic support. That would move the bill further to the left, meaning conservatives would not get nearly the level of tax cuts they want, and certainly no spending cuts. In the Senate, a vast majority of Democrats have told Trump and Republican leaders that, unlike on their drive to repeal Obamacare, they would be willing to collaborate on tax reform as long as the bill benefits the middle class more than the wealthy and does not add to the deficit. But Majority Leader Mitch McConnell quickly rejected their entreaty, saying Republicans would pursue the party-line reconciliation process instead. “I don’t think this is going to be 1986, when you had a bipartisan effort to scrub the code,” McConnell told reporters.