The closed-door process under which Republican congressional leaders and the Trump administration are crafting an overhaul of the United States tax code could impede the Senate’s timeline for the effort.

Lawmakers say they have yet to receive key details, making it difficult to craft a fiscal 2018 budget resolution that will ultimately serve as the vehicle to advance the tax bill.

“From my standpoint, it probably pushes it back in terms of when you pass a budget resolution,” Wisconsin GOP Sen. Ron Johnson said. “We need some kind of indication, and some sort of feel of a consensus within the Senate and House conferences in terms of how much static loss in revenue are people willing to tolerate.”

While there is a renewed commitment to get a tax overhaul complete this year, Republican senators expressed concern that the secretive process that ultimately doomed the effort to repeal the 2010 health care law will happen again.

“Health care should teach us something around here. If you don’t have a plan, you make it up as you go, you’ll wind up failing. Learn something from health care,” South Carolina Sen. Lindsey Graham said Thursday.

The group known as the Big Six that has for months been working on the tax overhaul measure behind closed-doors includes Senate Majority Leader Mitch McConnell, Senate Finance Chairman Orrin G. Hatch, House Speaker Paul D. Ryan, House Ways and Means Chairman Kevin Brady, Treasury Secretary Steven Mnuchin and top White House economic adviser Gary Cohn.

While members of that group say they have made good progress, Republican senators have yet to receive any substantive information about it.

“Damned if I know,” Arizona Sen. John McCain said when asked when he expected to hear more details. “We need to have it out and the focus has got to be the regular order.”

When asked if he is concerned about the lack of information, Sen. Steve Daines replied, “Always.”

“It’s hard to prepare without details,” the Montana Republican said.

Health care comparisons

The phenomenon is somewhat of a deja vu one for Senate Republicans. McConnell crafted the bill to overhaul the health insurance system in total secrecy, which led to widespread criticism and ultimately played a role in the demise of the effort.

While lawmakers say the early involvement of the White House and coordination between the House and Senate is positive, several said it could make advancing the legislation quickly more difficult.

Other said they feel more confident after receiving some early information from the Trump administration.

“I attended a meeting the other night, which one of the Treasury officials gave a brief overview, but it wasn’t specific,” Republican Sen. Susan Collins of Maine said.

The House and the Senate both intend to bring the tax overhaul through regular order, including holding committee hearings — a process that was nixed on the Senate side for the health care effort.

Efforts on taxes endure

But Republicans still intend to try to pass the tax legislation through the budget reconciliation process, which allows for passage with only a simple majority. To do that, however, Congress must first past a budget resolution and subsequent reconciliation instructions, something lawmakers say is difficult to do without details on the tax effort.

“Before we pass a resolution that would give us the ability to pass tax reform under reconciliation, it would be nice to have a little bit more of a consensus about what the tax plan would be,” Johnson said. “I really do think we need a little more work, a little more detail from the administration, House Ways and Means and Senate Finance, before we really create that budget.”

When asked what details he has seen so far, Johnson said, “Not enough.”

Other members of the Senate Budget panel voiced similar sentiments.

“If you’re on the Budget Committee, looks like you would know something about the plan. How do you write a budget reconciliation instruction if you have no idea what the contours of the plan are? Other than that, things are great,” Graham said.

The Senate Budget Committee met Thursday to discuss the fiscal 2018 budget. When asked for his takeaway from the meeting, Graham said, “Nobody has any idea what the plan is.”

Key decisions, such as what method to use to analyze the economic impact of the tax legislation and what effect the plan will have on the deficit, have yet to be determined.

All of this has irked a conference that is on edge after a devastating defeat in their attempt to repeal former President Barack Obama’s signature domestic achievement.

Lawmakers are even preparing backup plans in the event of another fiasco similar to the health care effort. One member, speaking on background to discuss legislation not yet introduced, said they had a separate proposal analyzed by the Congressional Budget Office to have the information ready to pitch it to their colleagues.

Senate Republican leadership, however, remains confident in the timeline for the tax overhaul.

“We’ve literally been talking about this for a couple years. So there does need to be some coalescing behind a single plan, but I expect to see that happen pretty soon,” Majority Whip John Cornyn of Texas said.