WASHINGTON — Republican lawmakers are increasingly at odds with Donald Trump across a range of high-profile domestic and national security issues, an early sign that the GOP-led Congress might resist some elements of the president-elect’s unorthodox agenda.

Although Trump maintains enthusiastic backing in many corners of the party, key members of the Senate and House have been outspoken in challenging his views of Russia and its interference in the U.S. election, warning of potential conflicts of interest arising from Trump’s far-flung business interests if he does not fully divest from his company, and criticizing the tough approach that he has taken to some companies, including his threat to impose a stiff tariff on firms that move jobs overseas.

No issue has so clearly divided Trump and top Republican lawmakers as much as his dismissal of U.S. intelligence agencies that attributed the hacking of the Democratic National Committee and other political targets to Russian operatives. The tensions were exposed over the weekend, as Trump belittled the CIA following a Washington Post report that the agency believed that Moscow favored Trump in the election while several Republicans, including Sen. John McCain of Arizona, joined with Democrats to call for an investigation into the matter.

“The Russians are not our friends,” Senate Majority Leader Mitch McConnell, R-Ky., told reporters Monday, voicing his support for an inquiry.

McConnell also appeared to break with Trump on the CIA, saying he has “the highest confidence” in the intelligence community and the CIA is “filled with selfless patriots, many of whom anonymously risk their lives for the American people.”

Sen. Susan Collins of Maine, a Republican member of the Senate Intelligence Committee, said Monday that a bipartisan congressional inquiry “could be useful toward achieving an objective accounting of any alleged meddling by foreign adversaries.”

In an interview on CNN Monday, Maine Sen. Angus King, an independent, told an interviewer that we need to have hearings in part because it will help show the American people proof of Russia’s influence.

“This is really serious,” he told CNN. “What if they had parachuted eight guys into Washington and broke into the building and carried the computers out under their arms? That’s effectively what they did. This is an attack on democracy and it’s absolutely consistent with what they’re doing around the world.”

Taken together, the tensions between the president-elect and fellow Republicans on Capitol Hill reflect a major test for how the GOP congressional majorities will handle the unusual circumstances of the Trump era.

Republicans, many of whom opposed Trump during the presidential primaries, want to work with him in many areas and avoid alienating his enthusiastic voter base. Yet some in the GOP are also assessing how to fulfill their constitutional duties as a check on a businessman-president who is unaccustomed to the public scrutiny inherent to a democratic system and unconcerned with past traditions of transparency, particularly when it comes to his personal finances. They also must prepare for the potential that Trump, who has effectively harnessed Twitter to skewer his critics, could turn his ire toward them.

Democrats, for their part, have little power to investigate Trump or thwart his nominations. In 2013, Democrats – angered by what they described as years of Republican obstruction – voted to scrap the rule requiring at least 60 senators to approve a procedural hurdle and move to a final confirmation vote. Now, all of Trump’s nominees for the executive and judicial branches, with the exception of picks for the Supreme Court, can be confirmed on a simple-majority vote.

With 48 seats in the Senate, Democrats in that chamber need to win over only a handful of Republicans to block a nominee, though doing so requires a degree of Democratic unity. That could be difficult, with 10 of the party’s senators facing re-election in two years in states that Trump won.

Incoming Senate Minority Leader Charles E. Schumer, D-N.Y., and his leadership team have urged senators set to serve as ranking members on top national security, financial and domestic-policy committees to focus on hiring professional investigators able to quickly dive into the personal and financial backgrounds of Trump’s nominees, according to a senior Democratic aide. The hope is that Democrats will be able to dig up dirt on Trump’s nominees just as Republicans did to some of President Barack Obama’s high-profile nominees in the early days of his administration.

The larger drama is likely to take place among congressional Republicans, who will face pressure to help Trump. So far, House Speaker Paul D. Ryan (Wis.) has demonstrated a reluctance to challenge the president-elect on some of the issues that have animated his GOP colleagues.

On Monday, Ryan dismissed calls for a probe into Russian meddling in the election, saying the House Intelligence Committee is “working diligently on the cyber threats posed by foreign governments and terrorist organizations.” He also appeared to criticize suggestions that Russia favored Trump, saying in a statement that “exploiting the work of our intelligence community for partisan purposes does a grave disservice to those professional and potentially jeopardizes national security,” and “we should not cast doubt on the clear and decisive outcome of this election.”

Ryan also has waved off concerns about Trump’s potential conflicts of interest related to his global real estate and branding empire. Asked last week by a CNBC interviewer how he hoped the president-elect would handle his business after he takes office, Ryan said, “However he wants to.”

“This is not what I’m concerned about in Congress,” he said.

Trump had planned a news conference Thursday to reveal how he will handle the business while he is in office, but his transition team said Monday that he will do it next month. Trump has hinted that he will retain an ownership stake while putting his adult children in charge of the company’s operations, telling “Fox News Sunday” that “essentially I’m not going to have anything to do with the management.”

Ethics experts and lawmakers in both parties have warned that if Trump retains his stake, he will face congressional hearings and, potentially, investigations into whether he has a direct and personal financial stake in the decisions he is supposed to be making in the public interest. They say that Trump’s refusal to release his tax returns has left the public largely in the dark about the full extent of the potential conflicts.

“Turning it over to his family and him still being a recipient of fruits of their labor does create conflicts in my mind,” said Graham, the GOP senator from South Carolina. “It will cloud his presidency if he doesn’t find a solution that puts it behind him.”

Rep. Mark Meadows, R-N.C., a member of the House Oversight Committee and the new chairman of the conservative Freedom Caucus, told The Post last week that he expects Trump to divorce himself from the business “as much as you can have a blind trust and fully divest.”

“He has more counselors around him, with plenty of law degrees, that will give him great counsel on how to stay out of trouble,” Meadows said. He added that he expected Trump to build the proper firewall, but that “we have an oversight function that would be appropriate, and from my standpoint I think it’s incumbent upon the Oversight Committee to look at everything without a partisan lens.”

The chairman of the oversight panel, Rep. Jason Chaffetz, R-Utah, said it was premature to consider any sort of investigation, but he said the committee would provide “vigorous oversight” of the new president.

“He’s still a private citizen at this point, though he needs to get his affairs in order,” Chaffetz said. “Give him a little breathing space, I think that’s fair.”

Ethics experts have called for Trump to appoint an independent trustee, unconnected to his family, to lead an effort to sell his assets and reinvest the proceeds without his knowledge. Trump has appeared to brush off concerns about conflicts, noting that there is no legal requirement that he separate.

“When I ran, everybody knew that I was a very big owner of real estate all over the world,” Trump told Fox News’s Chris Wallace in an interview that aired Sunday. “I mean, I’m not going to have anything to do with the management of the company. You know, when you sell real estate that’s not like going out and selling a stock. That takes a long time. . . . I’m going to have nothing to with it. And I’ll be honest with you – I don’t care about it anymore.”

Trump said he was “turning down billions of dollars of deals” as he prepares to take office. “I’m not going to be doing deals at all,” he said. “Now that would be – I don’t even know if that’s a conflict. I mean, I have the right to do it. You know, under the law, I have the right to do it. I just don’t want to do it. I don’t want to do deals, because I want to focus on this.”

Several lawmakers who would be responsible for probing potential conflicts of interest said in recent interviews they are willing to give the incoming president time and space to figure out how he will deal with the situation.

“We haven’t even started the next Congress and we haven’t seen exactly how President-elect Trump is going to handle all this,” said Sen. Ron Johnson, R-Wis., who leads the Homeland Security and Government Affairs Committee with jurisdiction over investigations. “I’m going to give him and his administration time to figure out what, quite honestly, is a very difficult situation.”

In other corners of the GOP, lawmakers say the calls to investigate Trump are coming primarily from his political opponents.

“There are going to be detractors from Trump [who] are going to try to make it sound like all the conflict of interest and all of that, and I don’t think people are really concerned about that except just the activists you run into on the Hill,” said Sen. James M. Inhofe, R-Okla.

“If it’s going to be those who just hate Trump and are looking for something to do him in or lessen his effectiveness – that’s not going to happen,” he added.