But they quickly ran into a problem: President Donald Trump.
Publicly, Republicans recoiled at Trump's talk of mass voter fraud in the November elections, urging him not to use government resources to investigate a problem many in the party believe the president has vastly exaggerated -- and even Oversight Committee Chairman Jason Chaffetz said he wouldn't look into the matter. They dodged questions about whether Congress would appropriate billions of dollars to pay for Trump's wall along the border of Mexico.
Several pushed back at Trump's suggestion that he may seek to restart harsh interrogation techniques, including waterboarding, that are widely considered torture. And all this comes after Trump engaged in a fight with the media over the size of inauguration crowd, distracting from the focus of his ambitious legislative agenda at the start of his presidency.
The message many want the new President to take: Don't undercut yourself.
"Fighting over crowd size and things like that takes us off message," Rep. Adam Kinzinger of Illinois told CNN. "If I were advising him -- and he hasn't called me -- I'd advise him and his team to stay on message, which is jobs, jobs, jobs and manufacturing."
Funding the wall
Despite Trump's distracting tweets and comments, the party is trying to move quickly to unite their legislative agendas. In the private meeting Wednesday, House Speaker Paul Ryan told Republicans that the party is considering funding Trump's border wall with Mexico through a supplemental funding package focused on border security, according to multiple attendees.
Doing so could extricate the border fight from a bill that must pass to keep the government open.
But a number of Republicans are nervous about funding the wall, refusing to say if they'd back a plan to have taxpayers pay potentially billions of dollars for the project. Trump has repeatedly said he plans to have Mexico reimburse the US for the wall after initially just saying Mexico would pay for it, though many are skeptical that such an approach will work.
"When it comes to our budget, we'll have those discussions," said Georgia Rep. Doug Collins, refusing to say three times if he'd support Congress appropriating money for the wall.
Privately, Trump convinced Ryan to prioritize a package authorizing new infrastructure projects as part of a 200-day legislative agenda for the new administration, according to one of Trump's top allies, Rep. Chris Collins of New York. Many conservatives, including Senate Majority Leader Mitch McConnell, want the new infrastructure spending to be offset with spending cuts. McConnell made that case in a private White House meeting with Trump earlier this week, sources said.
Ryan also told members that the effort to boost infrastructure would come through various legislative proposals, such as upgrading airports, rather than one comprehensive bill, sources said.
"Initially, without the President's input, that would not have been the case," Collins told reporters. "Our President has been pretty clear on setting his priorities."
But some of his priorities have prompted pushback, including Trump's openness to reinstating waterboarding and other harsh interrogation tactics.
"Those issues are settled law," said Sen. John Thune, No. 3 in the Senate GOP leadership, referring to a ban on waterboarding. "Congress has spoken."
In a statement, Sen. John McCain of Arizona added: "The President can sign whatever executive orders he likes. But the law is the law. We are not bringing back torture in the United States of America."
Standing ovation for McConnell after Supreme Court move
Trump and Vice President Mike Pence are set to address congressional Republicans on Thursday here in Philadelphia. Ahead of the speeches, McConnell and Ryan, speaking privately to Republican lawmakers, laid out their legislative plans -- starting with repealing Obamacare, reforming the tax code, gutting regulations and confirming Trump's Supreme Court nominee.
But McConnell warned House Republicans not to get impatient with the deliberative nature of the Senate, saying there are limits to what his conference can accomplish with 52 members in a body where 60 votes are needed to get most things accomplished. Some House Republicans were not convinced.
Yet the mood was optimistic in the congressional meeting, attendees said. At one point, McConnell got a standing ovation when he said that it was his decision to leave the final Supreme Court seat vacant in the final year of Barack Obama's presidency, attendees said.
But with so many items left on the agenda, Republicans are eager for Trump to focus his energy on specific legislative initiatives -- rather than other matters, like his call for a "major" investigation into mass fraud during the elections.
Chaffetz dismissed the topic, telling reporters "On the voter fraud issue, that really happens at the county level. I don't see any evidence. But the President has 100,000 people at the Department of Justice and if he wants to have an investigation, have at it. I just don't see any evidence of it."
"The oversight committee is not planning to do anything with it. If the President sees that, he's got a 100,000 he can task with doing that."
"I think it's very important that people have confidence in the elections and the outcome of those elections," said Rep. Cathy McMorris Rodgers of Washington state, the No. 4 GOP leader in the House.
"I view the election as history, and we're ready to roll up our sleeves and go to work," Thune said.
Asked about whether they were concerned about the White House not coordinating with congressional Republicans on their message and rollouts, Thune chalked up the bumpy start to a new administration in "transition" and noted that even the House and Senate Republicans often find themselves on opposite pages.
"It's a work in progress," Thune said with a laugh, as he looked over at McMorris Rodgers.