Service Employees International Union Local 500 has created a petition urging management at the liberal watchdog group Media Matters for America to "walk the walk" on progressive values and stop opposing the unionization of its staff. It is the latest salvo in Local 500's nearly two-month-long effort to get MMFA to back collective bargaining.

"Employees at Media Matters have been organizing to form a union and join SEIU Local 500, but Media Matters executives have been fighting it every step of the way -- even though they claim to pro-union!" the petition reads.

The petition was announced by Local 500 on Thursday. The sign-up list itself is on By Monday, it had 148 signatures with a modest goal of just 200.

Local 500 first approached Media Matters in early April, hoping to get management to accept the union's claim that it had already gotten the support of majority of the nonprofit's staff through a card check election. MMFA refused, so the union filed a petition for an election with the National Labor Relations Board on April 10. The nonprofit then lawyered up, hiring attorneys with the firm of Perkins Coie, which specializes in representing management in labor disputes.

The union initially downplayed the conflict, stating that they believed they could still reach an agreement with Media Matters. Management continued to resist, however, and talks quickly deteriorated. On April 28, a group of MMFA employees calling themselves the "Media Matters Organizing Committee" issued a statement through Local 500 that they "feel betrayed" by management.

"The actions of Media Matters executives have placed employees in the impossible position of continuing to produce content espousing pro-labor values for an employer who is challenging our right to unionize. Not only is management subjecting Media Matters employees to arduous NLRB procedures, the actions of their attorneys indicate Media Matters executives object so tenaciously to our union that they appear willing to prevent employees from ever having the opportunity to vote on the matter," the staffers wrote.

Local 500 has apparently withdrawn its official NLRB petition for an election. Union spokesman Christopher Honey did not explain the reason for this but indicated that they were still pursuing representing Media Matters' staff.

"The situation is that their lawyers are continuing to push back and fight against a union," he said. Honey has previously claimed that 36 of MMFA's 51 staff members have signed cards saying they want to join the union.

Local 500 withdrew, then re-filed its petition regarding Media Matters last month. There are strategic reasons why a union might pull an election request. An NLRB petition can take a long time. Local 500 may think a public pressure campaign will be more productive.

Media Matters did not respond to a request for comment. In statement last month, spokeswoman Jess Levin said: "We respect the rights of our employees and will work through this process."

The liberal watchdog group, founded by David Brock in 2004 with funding from George Soros, has regularly presented itself as a supporter of organized labor. It has argued that "economists point to declining union participation as one cause of the growing economic rift in America" and claimed it was a fact that "unions increase productivity [and] do not reduce business competitiveness."