The staff of the American Civil Liberties Union has opted to form a union, employees say, making it one of the most high-profile nonprofit organizations to unionize in recent years amid a surge of organizing among younger workers in cities.

The union, which is calling itself ACLU Staff United, has cards signed by a supermajority of the staff and members are asking for their management to voluntarily recognize the unit, without pushing it to an election overseen by the National Labor Relations Board, union organizers said.

The bargaining unit will cover about 300 employees, mostly staff attorneys, communications personnel, organizers, and campaign strategists at ACLU offices in New York, Washington, San Francisco and Raleigh, N.C., union organizers said.

The ACLU, one of the country’s premier civil rights organizations, has grown substantially in the Trump years. It has filed more than 400 lawsuits against the administration over issues including the immigration travel ban, the border wall, family separations at the border and the exclusion of undocumented immigrants from the census, casework that has placed the organization at the center of efforts to resist large portions of the Trump administration’s agenda.

The ACLU’s union campaign is another sign of how organizing has become more popular with younger, highly educated staff members in industries with strong moral underpinnings, such as digital media and nonprofit organizations, think tanks and museums, and technology companies.

“The ACLU was formed around protecting speech and protecting labor unions during the Red Scare,” Gillian Ganesan, a union campaign strategist who works on the ACLU’s portfolio of work on policing issues and has been helping with the union effort. “That’s one of our core, outward-facing values. And so it feels natural and right for us to be collectively bargaining.”

A group of support staff members at the organization is already unionized with a local affiliate of the United Auto Workers.

A request to the ACLU for comment on the union effort was not returned on Wednesday morning.

Employees involved with the union’s formation said its top priority is addressing what they described as high turnover among ACLU staff members who are minorities. They also want to ensure retention and investment strategies for members of other groups, including those who are transgender or gender nonconforming, formerly incarcerated, is sound. Union organizers included those without Ivy League degrees in those groupings.

“We’ve been losing workers of color,” said Alejandro Ortiz, a senior staff attorney in the organization’s racial justice program, who has been helping to organize the union effort. “It’s alarming for everyone. We’ve heard all the right things being said by management, when that’s said, but from our perspective nothing concrete has come out of it. That has caused significant consternation.”

The ACLU did not respond to inquiries about these workplace claims.

Other reasons the organizers listed for the union’s formation included a philosophy about the importance of unions, working to increase transparency for decisions made by ACLU leadership, and earning workers a larger voice in the organization’s operations, as well as contractual issues such as wages, hours and benefits.

Union membership nationally has been on the decline for decades, but there has been an increase in energy among organizers in recent years as a younger and more liberal generation has helped bring more visibility to labor issues.

Small but influential sectors such as digital media and nonprofit organizations have been a bright spot for organizers, who have seen a wave of unionization course through workplaces in recent years, as a younger generation of workers has sought more say over work terms.

The ACLU’s membership more than quadrupled in the 15 months after the 2016 presidential election, and millions of dollars in donations have poured in.

But its uncompromising stance on free speech has occasionally drawn ire from the left in the heated emotions that often underscore the Trump era.

For example, its affiliate in Virginia represented the organizer of a white supremacist rally in Charlottesville in 2017 in a case against the city after it had revoked the organizer’s permit to demonstrate. The decision drew wide condemnation and at least one resignation from its board, after the march turned violent.

The group walked a careful line last week after President Trump was banned from most major social media platforms, saying it was concerned about the “unchecked power” of companies such as Twitter and Facebook.

But those types of decisions are not fueling the union effort at all, according to Ortiz, Ganesan and Lindsey Kaley, an ACLU staff attorney.

The ACLU unionized staff members would be affiliated with the Nonprofit Professional Employees Union (NPEU), which has been growing its ranks among nonprofit organizations and think tanks. Despite the progressive bona fides of many of these organizations, union campaigns have not always been welcomed in their offices.

Last year, at the ACLU’s affiliate in Kansas, management declined to voluntarily recognize the union formed by eight employees and hired a law firm known for fighting union efforts that argued the staff had no right to organize, according to the Kansas City Star. The contentious drive resulted in the union filing at least one complaint with the National Labor Relations Board.

Kayla Blado, the president of the NPEU, said she hopes the ACLU will voluntarily recognize the union.

Workers said the organization’s management was generally aware of the union effort, but there had been little formal communication about it besides an email over the summer from Anthony Romero, the executive director of the ACLU, that noted it.

The organization generally espouses workers’ rights and even includes a section on its website that outlines collective bargaining rights.

“The ACLU has championed the right of workers to organize unions since its inception more than 90 years ago,” it says. “The ACLU continues to support the rights of employees, both public and private, to organize unions and bargain collectively.”