House Republicans have taken the first step to keeping Donald Trump's push for "one big beautiful bill" alive this week with a budget resolution that will set the parameters of any deal.
But the challenge remains of making space for even a sliver of Trump's 17 different tax cut ideas.
The House of Representatives sent the resolution to the Senate in a narrow 217-215 vote on Tuesday, with just one lone Republican voting in opposition.
House Speaker Mike Johnson faced microscopic margins, caught between deficit hawks on one side and nervous GOP moderates on the other. Both camps seemingly were ready to tank the effort even before it gets fully underway.
"This is a prayer request," Johnson even quipped on Monday. "Just pray this through for us because it is very high stakes," he added of this week's effort, even as he expressed confidence Republicans could get it done.
"I don't think anyone wants to be in front of this train. I think they want to be on it," he added.
Underlying the problem for Johnson and his party is the unforgiving math — especially on the tax side of things — that has its roots in an array of promises from a freewheeling Trump.
Yahoo Finance counted more than a dozen tax pledges from Trump before last November's election. A recounting in recent days has upped the tally to 17 different ideas, almost all of them cuts.
Even the smallest estimates of Trump's varied tax promises put the tab at about $10 billion. The higher-side projections amount to much more: almost $18 trillion in new red ink over the coming decade.
Meanwhile, Johnson and his colleagues are putting aside space for, at most, $4.5 trillion for tax cuts as part of an overall bill that would be paired with about $1.5 trillion in spending cuts.
In addition to being nowhere close to enough to pay for Trump's tax ideas, the proposed cuts are also proving unpopular in their own right, as is the idea of potentially $3 billion in new red ink.
"The big question for me is whether the markets balk at that or not," Pangea Policy founder Terry Haines said in a recent episode of Yahoo Finance's Capitol Gains podcast of new deficit spending, adding, "Once the degree of deficit increase becomes clear ... the markets are going to have a question to answer about whether they want to support this or not."
Johnson faced the risk of two public GOP "no" votes — Reps. Tim Burchett and Victoria Spartz, who say spending cuts need to be deeper.
But other Republicans were also making noise about joining them and voting no for the opposite reason, saying some of the harsher cuts — especially in healthcare — might need to be reversed. Hours of persuasion by Johnson and No, 2 House Republican Steve Scalise reportedly swayed the holdouts to back the bill.
Democrats voted no en masse, with one abstention, calling the entire project a giveaway to the rich.
A tax plan left squeezed
The math still leaves House Republicans with an allotment for tax cuts that may not even be enough to cross off the first item on Trump's list: extending the expiring provisions of the 2017 Tax Cuts and Jobs Act.
An analysis from the nonpartisan Committee for a Responsible Federal Budget (CRFB) found that paying for that item alone could cost between $3.9 trillion and $4.8 trillion over the next decade.
White House press secretary Karoline Leavitt recently outlined Trump's eight top tax priorities.
They included extending that 2017 law, providing relief on state and local taxes (SALT), no taxes on tips or overtime pay or Social Security benefits, cuts in the corporate tax rate for domestic production, closing the so-called carried interest loophole, and reducing tax benefits for sports stadium owners.
The total tab for those ideas — even with the last two items on Trump's list representing tax increases — comes to somewhere between $5 trillion and $11.2 trillion, according to the CRFB.
Speaker of the House Mike Johnson speaks with reporters at the US Capitol on Feb. 24. (Kent Nishimura/Getty Images) ·Kent Nishimura via Getty Images
And that's without a host of other ideas that Trump expounded on the campaign trail but has downplayed more recently.
Such ideas — many of which remain popular in powerful corners of Capitol Hill — range from making car loan interest fully deductible to a new tax credit for family caregivers to a further expansion of the child tax credit.
The total tab is somewhere between $10-18 trillion in impact to the federal budget over the coming decade, according to estimates from both the CRFB and from the Yale Budget lab.
That means hard decisions — or some seriously fuzzy math — is in the offing as Republicans search for a way to fulfill perhaps their central 2024 promise in a world of $36 trillion national debt.
'We're about to enter a period of substantially more uncertainty'
But even the initial efforts to pay for it have left some moderate Republicans wary.
The budget blueprint set to be voted on this week has signaled that Medicaid could be in for $880 billion in cuts to the government healthcare program for low-income individuals and families.
That puts at risk a program that is heavily relied on by voters, even in Republican districts.
It's why Johnson and other Republican leaders are currently at risk of losing the vote of moderate figures such as Rep. Jeff Van Drew of New Jersey, among others.
An analysis from the left-leaning Center for American Progress found that Drew's district alone could lose up to $2.18 billion in Medicaid funding if the cuts go through, potentially jeopardizing healthcare for 50,000 of his voters.
President Donald Trump listens to a question during a meeting with French President Emmanuel Macron at the White House in Washington on Feb. 24. (LUDOVIC MARIN/POOL/AFP via Getty Images) ·LUDOVIC MARIN via Getty Images
Republicans also face a political imperative to find a path to some sort of deal after making tax cuts a signature 2024 campaign issue and major provisions of the 2017 law set to expire at the end of the year in what Republicans like to call potentially the biggest tax increase in history if no action is taken.
Haines currently pegs the odds of some sort of tax deal this year at 80% and predicts that ideas like no tax on tips ("the oldest ask from Trump") and increasing the SALT cap must be included in the bill because of their fierce political support.
The bill is "moving about as quickly as Washington can move," he said, noting that it could be a bumpy ride for markets in the short term, saying, "We're about to enter a period of substantially more uncertainty."
Ben Werschkul is Washington correspondent for Yahoo Finance.
Every Friday, Yahoo Finance'sRick Newman and Ben Werschkul bring you a unique look at how U.S. policy and government affects your bottom line on Capitol Gains. Watch or listen to Capitol Gains on Apple Podcasts, Spotify, or wherever you find your favorite podcasts.