It looks like we might not be getting that bright and shiny new jail after all. With a crucial Board of Supervisors vote on the project set for today, six Supervisors have officially come out in opposition — and six is the magic number needed to tank the estimated $380 million project.

The Examiner notes that Supervisors John Avalos, Eric Mar, Jane Kim, and David Campos have been consistently opposed to the new jail — with Supervisor Kim going so far as to pen an op ed in the Chronicle arguing her case — and reports that both Supervisors London Breed and Malia Cohen yesterday came out in opposition.

The new jail was to replace the current (seismically unsafe) jail at the Hall of Justice, and was set to be helped along with $80 million in state funding. However, with the inmate population decreasing, progressives on the Board argued that money would be better spend on preventative measures and treatment programs.

Mayor Ed Lee and Sheriff-elect Vicki Hennessy support the new jail.

Newly elected Supervisor Aaron Peskin, who some believed could wind up as the swing vote on the jail, today told the Examiner that he is "still learning" about the issue.

The San Francisco Chronicle reports that the American Civil Liberties Union and thirty other organizations teamed up to send a letter Monday to the Board and the mayor opposing a new jail.

"Our current jail is fifty percent empty," reads the letter in part. "San Francisco has decreased its jail population by thirty-five percent over the past ten years, and crime in the city is down.

"Many of the people currently in San Francisco jail need psychiatric care," the letter continues. "The city has an excess of jail beds, but we have long waiting lists for residential mental health treatment beds."

If the proposed new jail does indeed die today at the Board of Supervisors, the inmates currently housed in SF's Hall of Justice jail would need to be shifted to one of three other jails in San Francisco.

Update, December 16: As expected, the Board of Supervisors yesterday voted against the new jail project. Surprisingly, the vote was unanimous, though as the San Francisco Chronicle reports the Supervisors did not actually reject the $80 million in state funding for the jail project — a fact which may have helped convince those previously in support of the project to vote with the progressive majority in opposition.

Sheriff-elect Vicki Hennessy, a vocal supporter of the proposed new jail, told the Chronicle that yesterday's vote could make San Francisco's existing jails less safe.

“I am concerned that we are going to be in the position of overcrowding the remaining jails ... and forced to make decisions about classification that may result in those facilities being more dangerous and difficult to manage,” she explained.

Related: Does San Francisco Need A New Jail?