It's what congressional Republicans had long dreamed about: a majority in both chambers to advance conservative policies and a president from the same party to sign them into law.
But the Trump White House isn't turning out exactly the way they envisioned.
The GOP establishment is experiencing whiplash after a week of President Trump bulldozing through the norms of policy and protocol — dashing off executive orders without warning, escalating a diplomatic crisis with the country's closest southern neighbor, triggering global confusion with a new refugee policy and generally hijacking party leaders' agenda and replacing it with his own.
Rather than the hoped-for collaborative new relationship between the White House and Congress, GOP officials complain that Trump is brushing aside their advice, failing to fully engage on drafting tough legislative packages like tax reform and Obamacare, and bypassing Congress by relying on executive actions, something they frequently complained about under President Obama.
At the same time, Trump's unilateral moves continue to blindside Republicans and direct the national focus toward topics many in the party would rather avoid, whether that's how to pay for building the border wall with Mexico, warming ties with Russia, investigating false claims about voter fraud or, most recently, implementing sweeping new policies on refugees and visas.
In the name of party unity, many Republicans so far have refrained from publicly attacking the new president. But for some, the new refugee policy crossed the line, signaling the first major rift in their already fraught partnership.
"It's unacceptable," said Sen. Jeff Flake of Arizona, one of the few GOP lawmakers critical of Trump's actions.
"We need to be careful as we do this," warned Senate Majority Leader Mitch McConnell said. "We don't have religious tests in this country."
Trump responded testily with two Sunday afternoon tweets aimed at Sens. John McCain (R-Ariz.) and Lindsey Graham (R-S.C.), who had issued a statement that day criticizing the "hasty" implementation of the policy.
"The joint statement of former presidential candidates John McCain & Lindsey Graham is wrong — they are sadly weak on immigration. The two… Senators should focus their energies on ISIS, illegal immigration and border security instead of always looking to start World War III."
For a party that lambasted Obama's reliance on his "pen and phone" to bypass congressional roadblocks, Trump's willingness to go it alone is testing the legislative branch's resolve to protect its power and maintain influence in the Trump era.
Lawmakers appear to have little forewarning of what Trump is doing from one day to the next — or even hour to hour — learning about their party leader's latest moves the way everyone else does — when his tweets light up their smartphones.
"This is obviously a transition that's underway here," said Sen. John Thune of South Dakota, the No. 3 Republican in the Senate. "There are issues where there are going to be differences of opinion between the White House and the Congress…. What we have to try and do is focus on the things that unite us."
Perhaps nowhere was the political adjustment more on public display than at the congressional Republican retreat in Philadelphia last week as Trump's controversial pronouncements ricocheted up the Acela corridor from the White House.
Republicans who had hoped to huddle privately to craft a policy agenda were forced to veer repeatedly off message as they fumbled to respond to Trump's string of actions and statements.
Many were dismissive about some of Trump's moves, particularly his push for an investigation into unsubstantiated claims of voter fraud in the 2016 election. "Have at it," said Rep. Jason Chaffetz (R-Utah), the House Oversight Committee chairman who said his committee had no plans to look into the matter.
Rep. Adam Kinzinger (R-Ill.) admitted to reporters he was barely able to keep up with the string of policy initiatives coming from the White House, and cautioned that Trump's approach might alienate Congress and others.
"You're taking your eye off the message and harming your ability to unify Republicans in the country," Kinzinger said.
Asked about Trump being a different kind of president, Sen. Jim Risch (R- Idaho), a former governor, quipped: "You think?"
"Both the president and Congress are adjusting," he added.
Republicans have spent the last decade trying to climb back to power since President George W. Bush was in the White House and they lost control of Congress.
Usually an election that puts the same party in control of both Congress and the White House would open the door to coordination and cooperation between the executive and legislative branches, which could seize the rare opportunity to muscle their priorities into law.
For example, Obama used such a period to pass the Affordable Care Act, an economic stimulus package and financial reform.
But few Republicans expected Trump would win the White House, so they didn't prepare a cohesive legislative agenda. They have been playing catch up ever since with a president who has no government experience, is unfamiliar with the lexicon of legislating and so far has had no qualms about leaving Congress in the dust.
Much time has been spent behind the scenes trying to bring the president up to speed on how to transform his popular campaign slogans — build the wall; bring back American jobs; destroy Islamic State — into actionable policy. But it remains a work in progress.
Some signs of morphing — and splintering — have emerged as each side steps up for a dance with the other.
When Trump suggested Congress should pony up money for his promised border wall to deter illegal immigration — on his word that Mexico would ultimately repay the cost — Republicans signaled support, even if it means they initially add to the deficit.
It was a stunning reversal for a party generally loath to pile on debt, having refused funds in the past for hurricane victims.
At the same time, Trump appeared to inch closer to Republicans by suggesting funding for the wall could come through a so-called border-adjustment tax, something GOP leaders have been pushing as part of corporate tax reform.
But the administration's position is unclear. Trump initially criticized the idea as too complicated, then the administration seemed to endorse it and then backed away, saying it was only one idea under consideration.
At the same time, as lawmakers struggle to figure out a replacement plan for Obamacare, they have received little help from the White House in shaping the details of such a plan.
Many Republicans appeared both enthralled with the prospect of swift, bold action after so many years of gridlock, and wary of an untested executive asserting power over the legislative branch.
"The strength of our government is three branches," said Risch. "All three of those are important, and if everybody stays in their own lane, it works better."
At the retreat, Trump gave a nod to the role Congress will play in the coming months. "This Congress is going to be the busiest Congress we've had in decades — maybe ever," he said, drawing cheers when he added that House Speaker Paul Ryan (R-Wis.) is "writing his heart out" with legislation.
But even Ryan was circumspect about what is possible this year. Congressional leaders pushed aside the traditional 100 days agenda in favor of one that will be 200 days.
"We don't want to set arbitrary deadlines on things," Ryan said. "It's going to take more than simply 100 days."