After months of sometimes bitter wrangling between the staff and management, workers for the liberal media watchdog group Media Matters for America voted Monday to join the Service Employees International Union.

"I am thrilled that the employees at Media Matters have chosen to join us at SEIU Local 500. Nonprofits like Media Matters have always been an important part of the larger progressive movement – now their employees are joining their colleagues at organizations like Public Citizen, Oxfam and the United States Student Association as a growing part of the labor movement," said Merle Cuttitta, the local's president, in a statement posted on its website.

The statement also quotes MMFA President Bradley Beychok: "We have always respected the rights of Media Matters employees to organize and collectively bargain. We look forward to the next steps in this process and thank our staff and allies in the progressive community for their support." MMFA spokeswoman Jess Levin confirmed the statement.

The workers voted "overwhelmingly," the local claims, without giving a specific number. MMFA reportedly has 51 employees.

It wasn't always this convivial. When Local 500 first approached MMFA in early April, management rejected the union's claim to have won the support of a majority of the employees through a Card Check election. The nonprofit then hired attorneys from the law firm Perkins Coie, which specializes in representing business in labor disputes.

Local 500 filed two petitions with the National Labor Relations Board demanding a workplace election but subsequently withdrew both, opting to focus on a public campaign instead.

In late April, a group of nonprofit's employees dubbed the Media Matters Organizing Committee issued a statement claiming that they "feel betrayed" by MMFA's opposition to letting them unionize.

"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," the committee said in a statement posted on Local 500's website.

The following month, Local 500 started a petition campaign on, calling on MMFA to "walk the walk" on progressive values and stop opposing the unionization of its staff.

Throughout the union's campaign, the normally pugnacious MMFA was tight-lipped, issuing terse statements that they supported their employees' rights without discussing the matter further.

That's all behind them now. In its statement today, the committee said: "We are pleased that the employees of Media Matters have elected to form a union, and we look forward to working with management to establish our first contract. The Organizing Committee and our supporters are deeply committed to the mission of Media Matters, and we know that having a union will make our organization stronger."