The signs of popular dissent from President Trump’s opening volley of actions have been plain to see on the nation’s streets, at airports in the aftermath of his refu­gee and visa ban, and in the blizzard of outrage on social media. But there’s another level of resistance to the new president that is less visible and potentially more troublesome to the administration: a growing wave of opposition from the federal workers charged with implementing any new president’s agenda.

Less than two weeks into Trump’s administration, federal workers are in regular consultation with recently departed Obama-era political appointees about what they can do to push back against the new president’s initiatives. Some federal employees have set up social media accounts to anonymously leak word of changes that Trump appointees are trying to make.

And a few government workers are pushing back more openly, incurring the wrath of a White House that, as press secretary Sean Spicer said this week about dissenters at the State Department, sends a clear message that they “should either get with the program, or they can go.”

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At a church in Columbia Heights last weekend, dozens of federal workers attended a support group for civil servants seeking a forum to discuss their opposition to the Trump administration. And 180 federal employees have signed up for a workshop next weekend, where experts will offer advice on workers’ rights and how they can express civil disobedience.

Then-Deputy Attorney General Sally Yates at the Justice Department on May 15, 2015. (Evelyn Hockstein/For The Washington Post)

At the Justice Department, an employee in the division that administers grants to nonprofits fighting domestic violence and researching sex crimes said the office has been planning to slow its work and to file complaints with the inspector general’s office if asked to shift grants away from their mission.

“You’re going to see the bureaucrats using time to their advantage,” said the employee, who spoke on the condition of anonymity for fear of retaliation. Through leaks to news organizations and internal complaints, he said, “people here will resist and push back against orders they find unconscionable.”

The resistance is so early, so widespread and so deeply felt that it has officials worrying about paralysis and overt refusals by workers to do their jobs.

Asked whether federal workers are dissenting in ways that go beyond previous party changes in the White House, Tom Malinow­ski, who was President Barack Obama’s assistant secretary of state for democracy, human rights and labor, said, sarcastically: “Is it unusual? . . . There’s nothing unusual about the entire national security bureaucracy of the United States feeling like their commander in chief is a threat to U.S. national security. That happens all the time. It’s totally usual. Nothing to worry about.”

The permanent bureaucracy, the backbone of the federal government and the bulwark against many presidents’ activist intentions, is designed to be at least a step removed from the crosswinds of partisan politics.

But for years, many conservatives have argued that the federal bureaucracy is stacked against them, making it harder for them to get things done even when they control the White House, Congress or both.

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Former House speaker Newt Gingrich (R-Ga.), a Trump adviser and longtime critic of the bureaucracy, said the pushback against the new administration reveals how firmly entrenched liberals are and how threatened they feel by the new regime. He cited an analysis by the Hill newspaper that showed that 95 percent of campaign donations from employees at 14 federal agencies went to Hillary Clinton last fall.

“This is essentially the opposition in waiting,” Gingrich said. “He may have to clean out the Justice Department because there are so many left-wingers there. State is even worse.”

Gingrich said Trump might push for civil service revisions to make it easier to fire federal workers. He predicted that the public would back the president over federal employees.

The signs of resistance in federal offices range from low-level grumbling and angry opposition posted online to anonymous promises of outright insubordination as new policies develop.

The State Department has emerged as the nexus of opposition to Trump’s refugee policy, in part because it has an official dissent channel where Foreign Service employees can register opposition without fear of reprisals. The channel, formed in 1971, has been used to raise policy objections to the Vietnam War and other conflicts. Several hundred employees signed the dissent cable objecting to Trump’s refugee policy.

Secretaries of state have taken the dissent channel so seriously that they have altered policies in response to complaints. In 2002, then-Secretary Colin Powell presided over the awarding of a prize for “constructive dissent” to an employee who had pushed back against a deputy secretary.

But State Department employees are nervous enough now that the American Foreign Service Association on Tuesday sent out an advisory called “What You Need To Know When You Disagree With U.S. Policy.” The note spelled out employees’ legal protections but warned that “walking out in protest of a U.S. government policy, even just temporarily, would be considered a strike” and can result in being fired.

Other agencies that lack that kind of tradition are in more turmoil. When the White House last week ordered an end to all advertising and other outreach activities encouraging Americans to sign up for health plans through Affordable Care Act marketplaces, employees at the Health and Human Services Department protested, pointing out that the ban on ads and robo-calls would probably result in less coverage of the most desirable customers — young and healthy adults whose scant use of medical care can help lower prices for everyone else.

The internal protest, combined with an outcry on social media and from the insurance industry, prompted the Trump administration to revise its directive in less than 24 hours.

Leaders of government workers unions and other associations say their members will do their jobs professionally and energetically, even if they disagree with the president’s politics or methods.

“There is no evidence we are seeing of a widespread federal bureaucracy revolt,” said Bill Valdez, president of the Senior Executives Association, a nonprofit that advocates for career federal managers. He said many managers are telling workers, “Don’t get involved in the drama happening elsewhere.”

The new administration’s talk of swift changes in the role and scope of some departments has frustrated many workers, said Randy L. Erwin, president of the National Federation of Federal Employees, but although “federal workers are now extremely concerned . . . federal workers are used to seeing the political winds change direction.”

Workers at some agencies say they have seen no sign of opposition. At the Education Department, which Trump at one point suggested be dismantled, one official said the new administration has been surprisingly agreeable: no major changes in policy, no troubling directives. “We’ve been, I think, heartened by how things are going here,” the official said.

But the level of worry is particularly high at places such as the Environmental Protection Agency. The head of that agency’s union got an email Tuesday from a local union leader asking for guidance on what to tell workers to do “if they receive an illegal order from management.”

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The union representing scientists and other EPA employees is exploring the formation of a fundraising arm to “defend federal scientists we anticipate will be disciplined for speaking out or for defending scientific facts,” particularly about climate change, said Nicole Cantello, vice president of Local 704 of the American Federation of Government Employees, which represents EPA workers in the Chicago area.

John O’Grady, a career EPA employee who heads a national council of EPA unions, said Trump’s firing of acting attorney general Sally Yates on Monday night after the Obama-era holdover had refused to implement Trump’s refugees ban “sends kind of a chilling effect through the agency. I’m afraid at this point that many federal employees are just fearful for their jobs, and they want to keep their heads down.”

Two Twitter feeds, @altUSEPA and @ActualEPAFacts, have attracted more than 200,000 followers and call themselves part of “the Resistance.” They appear to be run by outside activists, rather than agency employees.

Top EPA officials have tried to reassure anxious employees. In an email to employees, Don Benton — a top Trump adviser to the EPA — insisted that media reports of crackdowns on public speech and scientific autonomy were “just not accurate. . . . Changes will likely come, and when they do, we will work together to implement them.”

In any administration, one man’s principled resistance is another’s outrageous defiance. Sen. Jeff Sessions (R-Ala.), Trump’s nominee for attorney general, said in 2015 that it is the obligation of a federal worker to stand up against improper orders.

In a confirmation hearing for Yates, Sessions said: “You have to watch out, because people will be asking you do to things you just need to say no about. . . . Like any CEO, with a law firm — sometimes the lawyers have to tell the CEO: ‘Mr. CEO, you can’t do that. Don’t do that.’ ”

Presidents appoint the heads of agencies and a few officials at the top of each department, but the great majority of those who implement any administration’s agenda are civil servants who enjoy legal protections meant to encourage them to blow the whistle on fraud and corruption.

Short of formal whistleblowing, workers are finding small ways to express their opposition. At the Justice Department, some career civil servants asked their bosses whether they were allowed to protest their new president by marching or contacting a member of Congress. The answer was yes, if they did so on their own time and in their personal capacity.

The day after the November election, the department’s ethics office said workers could wear clothing that contained a political message. One lawyer who had worn a Hillary Clinton T-shirt beneath another layer of clothing said that once the advice was issued, “I took the layer off.”

In the past few days, protest accounts have popped up on social media from employees at several agencies. An immunologist who formerly worked at the Centers for Disease Control and Prevention created what he called a “resistance page,”@viralCDC, for CDC employees to post vaccine and public health information that workers believe the Trump administration may seek to remove from public view.

There has been no freeze on communications at the CDC, said spokeswoman Kathy Harben.

Similarly, a Twitter account protesting Trump’s policies has popped up in the Defense Department. Using the handle @Rogue_DoD, a service member has tweeted everything from Defense Department documents warning about the effects of climate change to an opinion piece accusing Trump of insufficient consultation with Defense Secretary Jim Mattis.

Career staff members in at least five departments said they are staying in close contact with Obama administration officials to get advice on how to handle Trump initiatives they consider illegal or improper.

Former labor secretary Thomas Perez, who also headed the Justice Department’s civil rights division under Obama, said he has not been in contact with his former employees but is working to mobilize grass-roots opposition.

“We’re mindful of our ethical responsibilities,” said Perez, who is running for chair of the Democratic National Committee. “We’re also mindful that we’re in an existential crisis.”

While many federal workers have begun to consider avenues of dissent only since the inauguration, others had been preparing for weeks. In the last days of Obama’s tenure, several departments catalogued data and reports and got them into the hands of allies outside the government.

The use of social media as outlets for worried government workers has spread through much of the bureaucracy. After Trump complained about the National Park Service using Twitter to compare the crowd sizes at his inauguration with the far larger assembly at Obama’s gathering in 2009, a gag order temporarily silenced the official social media account.

In response, an ex-employee at Badlands National Park who still had access to its Twitter feed started posting facts about climate change. The rogue tweeter won more than 60,000 followers before park officials regained control of the account.

Social media accounts have popped up to defend the Smithsonian Institution and the National Endowments for the Arts and the Humanities. Employees at some Smithsonian units have been reminded that policies prohibit them from using their work devices to post political comments.

“We don’t intend to change the way we do things,” said Smithsonian Secretary David J. Skorton. “That’s not out of a sense of defiance, it’s not out of a sense of not wanting to be accountable, it’s out of a sense of believing in the mission of the Smithsonian, which is to do research and share information with the public.”

Academics have debated for years whether bureaucracies inevitably grow to a point where they, as political scientist Michael Nelson of Rhodes College put it, “ineluctably overpower” their political masters. “Time and time again,” he wrote, “major efforts to make administration more responsive to political control have had the opposite effect. It is enough to chasten even the boldest reformer if, like the sorcerer’s apprentice, his every assault on his tormentors doubles their strength.”

Emma Brown, Lalita Clozel, Brady Dennis, Karen DeYoung, Darryl Fears, Anne Gearan, Amy Goldstein, Joe Davidson, Dan Lamothe, Peggy McGlone, Carol Morello, Ellen Nakashima and Lena Sun contributed to this report.