Vox Media Union, an affiliate of the Writers Guild of America East, said Thursday that it had reached an agreement with the owners of the liberal website Vox.com and seven other websites to represent their workers.

The announcement marks a growing trend of labor unions targeting liberal news organizations and nonprofit groups for organizing bids, something those groups' management have often resisted.

"On January 10, 2018, we reached an agreement with Vox Media’s management to obtain recognition for the Vox Media Union. We have worked hard to form a unit that represents the people who build this company every day and want to look out for each other. That work has finally paid off. We won recognition of our union thanks to our unity and resolve, and now we will have a seat at the table to advocate for the needs and priorities of creative staff," Vox Media Union said Thursday.

"Congratulations to everyone on this hard fought victory," tweeted AFL-CIO President Richard Trumka.

Vox Media is the parent corporation of Vox.com, a popular news and analysis website, as well as Curbed, Eater, Polygon, Racked, Recode, SB Nation, and the Verge. The union will represent workers at all of the sites as well as Vox Studio/Entertainment.

A representative of the company could not be reached for comment.

Late last year, the union had accused the company's management of "union busting," because it declined to accept the union's claim that it had majority support among the workers. Vox Media instead sought a federally monitored secret ballot vote to certify the union's claim.

"Even if there is a lot of support we want to ensure that all employees are able to make informed decisions about the union, and feel that their voices are heard too," the company said in a letter the union subsequently made public.

The organizers started an online campaign to shame the company's leaders to other liberals to get them to accept a union. They noted that in a 2006 article by Vox co-founder Ezra Klein in which he gave qualified support to "card check" elections, the term for when management agrees to forego a federally monitored vote and instead accept a union's claim of majority support. "My concerns fell much more with the current, constant, and far more effective intimidation tactics of employers," Klein said at the time. It is not clear what, if any, role Klein had in Vox Media's actions regarding the union bid.

Vox Media Union alluded to the earlier resistance in its statement Thursday. "Though it’s taken some time, we’re glad that Vox Media has lived up to its stated values and respected the wishes of its employees. We’re eager to get to the bargaining table and have a discussion with the company about how to make this place even better."

While traditional newspapers and other media companies have often been unionized, smaller liberal-leaning news organizations, nonprofits, and advocacy groups have generally not been. Unions have sought to reverse that in recent years, trading on the fact that the political views of the workers and management would make organizing easier. The unions have nevertheless faced significant resistance from the groups' management.

Media Matters for America was organized by the Service Employees International Union Local 500 in 2014 after a campaign that claimed "union busting." The same union is now attempting to organize the Council on American-Islamic Relations, which is also actively opposing the bid. Jonah Peretti, founder and chief executive officer of BuzzFeed, has opposed unionizing his company.