In the roiling debate over the plan to replace the Affordable Care Act, there’s a lot more at stake for President Trump than whether the bill can be saved: Its fate could also determine how much else he can get done on Capitol Hill in the early stages of his presidency.

With the bill facing strong resistance on multiple fronts, Trump’s effort to shepherd it through Congress is shaping up as a pivotal test of an un­or­tho­dox president’s ability to wield influence in Washington, a growing number of Republicans say.

A win on an issue as fractious as health care could serve as a rallying point for even tougher fights ahead, including some Trump agenda items that wouldn’t otherwise be GOP priorities and others that would likely require Democratic support.

But falling short on a marquee campaign promise — when both chambers are controlled by the president’s party — would almost certainly sap momentum for Trump’s agenda. Moreover, Republicans are counting on cuts from former president Barack Obama’s health-care law to make the budget math work on other Trump priorities, particularly major tax reductions.

(Daron Taylor/The Washington Post)

“It’s difficult to see the kind of aggressive agenda that they’ve outlined for the rest of this year without some sort of repeal-and-replace success,” said Michael Steel, a former senior aide to former House Speaker John A. Boehner (R-Ohio), referring to the House bill that seeks to scale back the health-care law, often called Obamacare.

The coming weeks, Steel said, “will show whether the Trump administration can use the tools of the White House to move legislation forward.”

[White House tries to salvage GOP health-care plan as criticism mounts]

As a candidate for president, Trump promised that he would work with Congress to pass legislation that would dramatically cut taxes, spur $1 trillion in infrastructure investments, significantly expand school choice and make it easier to afford child care. And he promised he would get started on all that — and six other pieces of legislation — in his first 100 days, according to a “Contract with the American Voter” released shortly before Election Day.

Now past the 50-day mark, only one of those bills — the House GOP health-care plan — has been introduced. And its path has grown more treacherous by the day, with mounting concerns about the millions of Americans projected to lose coverage, including many who supported Trump in last year’s election.

During his daily news briefing Tuesday, White House press secretary Sean Spicer said Trump remained open to improving the bill but emphasized the urgency of moving forward on a long-standing Republican promise.

“This is the only vehicle that seeks to achieve what people on our side of the aisle have been talking about since 2010,” Spicer said. “This is it. If we don’t get this through, the goal of repealing Obamacare and instituting a system that will be patient-centered will be unbelievably difficult.”

View Graphic What’s next for the Obamacare replacement bill

Trump’s voter contract, released in late October, included a slew of promised executive actions as well as 10 specific pieces of legislation that he said he would introduce and “fight for” in his first 100 days.

White House aides point to progress on several executive actions, including Trump’s second attempt at a travel ban targeting “terror-prone regions,” as the document describes them. But the only legislative initiative that can be checked off as introduced is the health-care plan. Even that bill would not do all that Trump advertised, which included reforms aimed at speeding the approval of lifesaving drugs and allowing the sale of insurance across state lines.

[The Fix: Some 64-year-olds would see premiums increase by 750 percent]

Other promised 100-day bills included a sweeping crackdown on immigration, including a southern border wall paid for by Mexico; a new system of tariffs to discourage companies from relocating abroad; and reforms aimed at reducing “the corrupting influence of special interests on our politics.” No such measures have been introduced.

A senior White House official said the document, modeled upon the “Contract with America” released by Newt Gingrich and other House Republicans during the 1994 midterm elections, remains a guiding light for the young administration.

The official, who spoke on the condition of anonymity to discuss White House strategy more candidly, said Trump aides are continuing to talk with Congress on all fronts and that pacing has more to do with “bandwidth” on the Hill than anything else.

“Clearly the longer it takes to pass one piece of legislation, the less time there is to pass other pieces of legislation,” the official said.

In the meantime, the official added, the executive branch is looking to make progress where it can without the assistance of Congress.

The official also disputed the notion that a defeat on health care would slow Trump’s momentum on other fronts. “Our plan is if you don’t succeed, try, try again — and improve,” the official said.

Republicans are taking up health-care legislation first in part because other parts of the president’s agenda hinge on elements of the tax code that would be altered by the law. Without those changes, tax cuts sought by Trump and House leaders become much harder to implement.

“It’s not just the momentum and fulfilling our promises; there are policy implications,” said one House leadership aide, who requested anonymity to speak candidly.

“There’s a sequencing that is important,” the aide said. “Without that, it makes tax reform extremely difficult, if not impossible.”

[Has Trump become the ‘don’t blame me’ president?]

Trump has promised to cut taxes on the middle class and to lower the corporate tax rate from 35 percent to 15 percent.

Another key to paying for those efforts is a House proposal for a “border adjustment tax” that would treat companies’ exports far more favorably than imports. Senate Republican leaders have been cool to the idea, however, and some GOP lawmakers are looking to Trump to bridge that divide.

Trump also has a major sales job ahead with members of his own party if he is to make good on a pledge to spur $1 trillion in infrastructure investments. The administration has yet to lay out a plan but has said it will rely heavily on public-private partnerships and tax incentives to keep the cost to the U.S. treasury in check. Still, many Republicans remain wary of what could be cast as a big-government spending proposal.

On those and other fronts, Trump could use leverage that would come with salvaging a health-care bill, several Republicans said.

“What the president is able to do here is pretty critically important for the rest of his agenda,” said Josh Holmes, a former chief of staff to Senate Majority Leader Mitch McConnell (R-Ky.). “If they can pilot that in for a landing, I think it bodes well for future activity.”

On the flip side, a defeat on health care will only embolden Democrats, whose cooperation Trump will need on several fronts.

“For Trump to fail would probably send a dagger through the heart of the rest of his legislative agenda,” said Jim Manley, who was a senior aide to former Senate minority leader Harry M. Reid (D-Nev.).

Sen. Charles E. Grassley (R-Iowa) agreed that “you won’t be doing any tax revision” if the health-care law fails, but he argued other goals were attainable.

Sen. Orin Hatch (R-Utah) said “it might embolden the Democrats if they can win on this issue. And we gotta make sure they don’t win on it.”

[Budget office bombshell is going to force changes to health-care bill]

Republicans are trying to pass the bill using a process known as “budget reconciliation,” a bill that does not require 60 votes in the Senate, which has 52 Republicans.

The effort to gut Obamacare threatens to tear loose the stitches that have held the Republican establishment and the conservative base together.

The president has said he is fully supportive of the bill crafted by Republican leaders, but he has also signaled being open to responding to conservatives’ concerns on some counts, including the timing of a phaseout of expanded Medicaid coverage.

That posture has led conservative activists to pin more blame on Congress than Trump for the bill’s rocky rollout — and provided some hope that the new president can still enact other priorities.

“I think it’s possible to get a ton achieved this year,” said Michael A. Needham, chief executive of Heritage Action. “It’s going to require a sense of openness and collaboration that we’re seeing from the White House and President Trump.”

Beyond Trump’s desire to make a show of action in the first months of his presidency, the intensive schedule is born of political necessity. Members of Congress facing reelection in 2018 are staring down the real prospect of backlash if none or only some of their agenda comes to fruition.

“Anytime you’re starting to legislate, your window of opportunity starts to close, especially in the House once you get closer to election year,” said the House leadership aide. “You need to move quickly to get things done.”

Karoun Demirjian and Kelsey Snell contributed to this report.