(Alice Li,Jayne Orenstein,Julio Negron/The Washington Post)

As Republicans reach the end of their first hundred days of controlling all the levers of power in Washington, the euphoria that accompanied Donald Trump’s unexpected presidential victory is giving way to realism about the limits of how much they can get done and how quickly.

They now acknowledge that having a president of their own party — even one who declared at last year’s GOP convention that “I alone can fix it” — is not the answer to everything for Republicans. To the contrary, being put in charge of both ends of Pennsylvania Avenue has brought to the surface the long-standing divisions within the party and tensions between the two houses of Congress.

Thus far, Republicans have failed to deliver on Trump’s most conspicuous promises of sweeping, swift change — as evidenced Thursday night by their second failure to even bring a health-care-law repeal to a vote in the House.

And they have come perilously close to that hallmark of congressional dysfunction, a government shutdown.

President Trump, accompanied by Veterans Affairs Secretary David Shulkin, right, and veterans, signs an executive order on "Improving Accountability and Whistleblower Protection" at the Department of Veterans Affairs on April 27. (Andrew Harnik/AP)

The difficulty involved in accomplishing something so basic as keeping the government’s lights on has raised concerns about whether the party is equipped to handle bigger challenges ahead. While lawmakers continued squabbling for a plan to fund the government for the remainder of this fiscal year, many worried that there is little work being done to prepare for the next one, which begins in October.

“Here’s what would be embarrassing: If the Republican House, the Republican Senate and a Republican president couldn’t pass a budget. That’s the biggest risk of all,” warned Sen. Lindsey O. Graham (R-S.C.).

Then there is the issue that motivates the GOP’s base like no other: repealing and replacing the Affordable Care Act. It is something Trump had promised would be “so easy” to get done “immediately. Fast. Quick.” Instead, the House stumbled Thursday in its second attempt to get a bill passed.

Dismantling social programs, even controversial ones, has proved harder than it looked to Trump and his fellow Republicans on Capitol Hill. Indeed, the proposal under discussion this week would leave much of President Barack Obama’s signature law in place.

“People underestimated how difficult that would be to achieve,” even with a GOP majority, said Rep. Tom Cole (R-Okla.).

Although being in power is preferable to the alternative, Cole added, “everybody sees the upside. Nobody sees the downside.”

Scrambling for elusive legislative achievements, Trump continues to add to the Republicans’ already overloaded legislative agenda. In the past week alone he has demanded that his sharply divided party in Congress not only step up the pace on a second health-care proposal but also push ahead on the first comprehensive tax overhaul in more than 30 years.

Tallying President Trump’s first 100 days

“Every day it seems there is another serious and substantial push coming out of the White House to be moving on initiatives, whether it’s taxes this week, trade or whatever. No one is sitting still,” said Sen. Lisa Murkowski (R-Alaska), who heads the Senate Energy Committee.

Meanwhile, Murkowski noted, there is much basic business that remains to be done, with the administration yet to even nominate people for many key positions.

“We’re still trying to get the president’s team filled out and help them with that,” she said. “Yet we don’t have any names.”

The difficulty is compounded by Trump’s ad hoc management style. He routinely changes course with the speed of a tweet, and sometimes he flat-out confuses his foot soldiers on Capitol Hill.

That was the case Wednesday, when many congressional Republicans were startled — and angered — by reports that Trump was considering an executive action to withdraw the United States from the North American Free Trade Agreement. By late evening, Trump had changed course, leaving it unclear whether the whole thing had been a real plan or a head fake.

In many respects, all of this reflects the fact that Trump as president is exactly what he promised he would be as a candidate.

He was serious in his declarations that he intended to blow up the old ways of doing things in Washington; the question for his second hundred days and beyond is whether the Big Bang that is underway in the nation’s capital will produce an enduring new order of the universe or simply more chaos.

Republicans have not been without their victories. Senate Republicans steered the surprisingly smooth and error-free confirmation of Neil M. Gorsuch to the Supreme Court and joined with the House to pass 13 bills undoing Obama-era regulations touching areas including gun policy, the coal industry and funding for Planned Parenthood.

But the days when Republicans could be rallied by their outrage against a Democratic president are gone. A governing party must produce — and can be easily undercut by its own factions.

For the initial effort to come up with a replacement for the Affordable Care Act, Trump outsourced the job to House Speaker Paul D. Ryan (R-Wis.). What the speaker came up with turned out to be something he could not sell to his own members.

When the process resumed this week, the White House took to negotiating directly on the issue with conservative and centrist factions of the House GOP conference. The bill picked up needed support from conservatives in the House’s Freedom Caucus, but it failed to pick up the necessary votes from House moderates.

Similarly, the new White House tax plan snubbed key elements of proposals introduced by congressional Republicans — most notably, the border adjustment tax on imports that Ryan and House Ways and Means Committee Chairman Kevin Brady (R-Tex.) had put forward as a centerpiece of their vision for overhauling the tax code.

“We’ve got all these deals that are being cut with individuals and small groups in smoky rooms, and folks like me don’t know what’s happening,” said Rep. Bill Flores (R-Tex.) “I think we have to get back where we have some transparency.”

A growing concern among Republicans in Congress is Trump’s tendency to lay down unrealistic deadlines, making demands for action within days on complicated policy questions that would take months to work through in anything close to a normal fashion.

And their majorities in Congress do not give Republicans complete command in Washington.

Conservatives in the House have grown frustrated with the Senate, where Republicans control a slim 52-to-48 majority and must turn to Democrats to pass most legislation.

“If the Senate blows it up, it’s their fault, not our fault,” said Rep. Scott Perry (R-Pa.). “We have to do our work diligently, and if the Senate screws it up, it’s on them.”

But South Carolina’s Graham argues that the Senate operates under the realities of arithmetic. “You don’t really have total control, and I want our base to understand that,” he said. “Democrats have a say. They can’t be dealt out. We’ve got to get enough of them to get 60 votes on big stuff.”

Republicans are indeed slowed by Democrats, who in the Senate have repeatedly made sure that debates over even noncontroversial Cabinet nominees drag out for as long as four days.

But it was Republicans who told the White House that money for a new wall on the U.S.-Mexico border would upend attempts to keep the government open after Friday — forcing Trump to abandon his demand, at least for now.

Still to be fought out is a touchier issue — whether the Trump’s tax cuts should be allowed to add to the deficit.

“The big question is how much of this tax reform will be paid for — totally, partially or not at all,” said Rep. Charlie Dent (R-Pa.), a leader of the centrist faction in the House.

Republicans in and out of Congress have also criticized Trump for failing to understand the pace and challenges of passing legislation in Congress.

“The White House has not yet learned to provide air coverage for Republicans to do the hard things on health care,” said Douglas Holtz-Eakin, the former head of the Congressional Budget Office and now president of the conservative American Action Forum.

Senior Republican aides acknowledged the challenges of the first few months of GOP rules, “but the same was true for the Democrats” when they had much bigger majorities on Capitol Hill than Republicans do now, said Don Stewart, a spokesman for Senate Majority Leader Mitch McConnell (R-Ky.).

With the exception of repealing and replacing Obamacare, “everything else that we’ve set out to do, we’ve done,” Stewart said.

Having total control of Washington “doesn’t mean they won’t bump heads,” added Grover Norquist, head of Americans for Tax Reform.

But even at the outset of their drive to rewrite the tax code, he said, Republicans have already achieved a broad consensus on some goals — including abolishing the alternative minimum tax, making drastic cuts to corporate rates and eliminating the inheritance tax.

“There’s no principled objection to what they want,” Norquist said. “I’m overwhelmed with how much everybody can agree on. The fights over particular things are not interesting to me.”

Perry, the Pennsylvania congressman, said he’s “not happy” with the outcomes of Republican control so far. But, he acknowledged, “I’m much more happy about it than what the first 100 days of a Hillary Clinton presidency would have meant.”