One of the nation's largest liberal media companies is in a showdown with organized labor.

Vox Media saw workers stage a one-hour walkout in May to protest slow-moving contract negotiations and now faces the prospect of a strike if it doesn't make a deal. On Thursday, the deadline for negotiations, the union announced that members are "not showing up to work today until we resolve" disputes over pay, severance, and subcontracting. Workers also published a photo on Twitter demonstrating their solidarity and sending a clear message to would-be scabs that they should think twice before crossing a picket line.

The Vox Union, which is part of the Writers Guild East, declined an interview request. Vox Media, which owns Vox.com and several other news media sites, did not respond to requests for comment.

The dispute took on new intensity when a study found that Vox Media's job postings shifted dramatically to contract or part-time workers after the company began recognizing the union in January 2018. Such workers fall outside the bounds of union representation.

"On the very date that Vox Media workers announced that they were seeking to join a union, that is, November 17, 2017, the company practically shut the door on hiring for full-time workers," the study found. Management at the company disputed the findings, saying "scraping of open roles on our website is not a sufficient measurement of full-time hires versus part-time and/or contractor roles."

Vox.com, the flagship site of the company, launched in April 2014 to help explain the news with infographics and charts put together by "the smartest thinkers" asking "the toughest questions." It has since become one of America's most highly visited media websites and attracted tens of millions of dollars from investors. Workers are asking for more generous severance packages in the event of layoffs, as well as pay increases tied to inflation.

"Our current merit-based system means salary increases are inconsistent. This must change, with guaranteed increases that match inflation, to ensure that Vox Media can employees maintain a reasonable living wage as the cost of living grows," the union said on Wednesday.

The dispute comes as a surprise given the publication has praised organized labor. Vox.com founder and editor-in-chief of Ezra Klein said unions and collective bargaining are the only way to stop capitalism from imploding due to inequality.

"Bargaining power is a crucial mediator in capitalism, and workers often end up with too little of it—and if that imbalance persists, then the entire system is imperiled," Klein wrote. "They've [unions] often saved capitalism from itself, and done so over the objections of the capitalists."