The perception that Oakland Councilmember Abel Guillén left the city’s largest public employees union in the lurch during contract negotiations starting last year, elicited a special type of pique for labor unions against the first-term councilmember.

In an email sent to the Alameda County Democratic Central Committee Wednesday, a progressive group of Oakland housing and social advocates are attempting an all out effort to block Guillén’s ability to gain the all-important backing of the local Democratic Party for the November elections. The party begins its endorsement process for Oakland races on Thursday night.

The email sent by Oakland Rising, a group that partners with some of the city’s most well-known housing and social advocates, including, the East Bay Alliance for Sustainable Economy (EBASE), Causa Justa, the Ella Baker Center for Human Rights, and the Asian Pacific Environment Network (APEN), among others, eviscerated Guillén for siding with developers as a councilmember, after once courting progressive advocates in order to get re-elected in 2014.

“This decision has been a long time in the making and hasn’t been reached easily,” Oakland Rising Executive Director Jessamyn Sabbag wrote to central committee members.

“After running in 2014 on a progressive platform rooted in economic justice, he sold out the community, betrayed their well-organized process, and put his own interests first to line his own pockets with the dollars of developers,” wrote Sabbag.

“We tried dozens of times to get his support of community-backed efforts such as the Protect Oakland Renters Act, the ReFund Oakland Budget Coalition proposal, East 12th Street proposal, Public Lands policy, Close the Loopholes policies, and many more. He consistently either declined to meet, refused to support our efforts, or tried to water them down until they were useless,” Sabbag continued.

Earlier this spring, community members, filed a complaint with the Oakland Public Ethics Commission over campaign contributions received by Guillén from individuals tied to the controversial East 12th Street Remainder land sale to developers, an issue so contentious in Oakland that it led to protesters shutting down a council meeting. The commission, however, found no wrongdoing.

Oakland Rising Action, the group’s political action committee, is backing Nikki Fortunato Bas in this fall’s District 2 race. Bas is the former executive director for EBASE, and has received endorsements from the powerful SEIU Local 1021 and California Nurses Association. In the email, Oakland Rising also advocates for county Dems to, instead, endorse Bas.

Receipt of the email by Alameda County Democratic Central Committee members comes just a day before the group is holding a candidates forum Thursday evening for Democrats running in Oakland’s mayoral contest and all three City Council races. The event, which is open to the public at the Elihu Harris State Building at 1515 Clay Street in Oakland, and begins at 5 p.m. to 9 p.m. The forums will be used by Alameda County Democrats to determine their endorsements in mid-September for the Oakland races.

NOTE: A correction was made to reflect that Oakland Rising has not endorsed Nikki Fortunato Bas. Instead, Oakland Rising Action, a political action committee, is endorsing Bas in Oakland’s District 2 council race.