 -- Attorneys representing a group of Bernie Sanders supporters informed San Francisco City Attorney Dennis Herrera Thursday night that they plan to file an "emergency request" with U.S. District Court Judge William Alsup in the city today "for a preliminary injunction" in California's June 7 presidential primary," Herrera's office said.

"I think it's unfortunate -- and selfish, frankly -- that these plaintiffs would inject confusion and uncertainty into an election that has been underway for weeks," Herrera said in a statement Thursday night. "San Francisco's Department of Elections and its employees have been doing an exemplary job, and I'm equally confident that our co-defendants are also meeting or exceeding their legal duties. This lawsuit is without merit, and there is no basis for an emergency injunction. I intend to fight it aggressively."

#BREAKING: Bernie #Sanders backers will seek emergency injunction in federal court on Friday, May 27, in #CAPrimary https://t.co/Dt6vMnh80g — SF City Attorney (@SFCityAttorney) May 27, 2016

Voting by mail began in California May 9.

A news release from the Office of the City Attorney, noted, "San Francisco, Alameda County, and state elections officials were sued last week by an unincorporated association of Sanders backers called the 'Voting Rights Defense Project,' who together with the American Independence Party and two San Francisco voters leveled an array of allegations in their May 20 civil complaint that Herrera calls wholly baseless."

The release continued, "The activists are seeking sweeping injunctive relief in their suit, including provisions to force 58 counties to segregate ballots already cast by unaffiliated voters; to allow "re-votes" by those voters for presidential primary candidates; and to extend the state's voter registration deadline -- which passed on May 23 for eligibility to vote in the June 7 primary -- until election day itself."

Bill Simpich, one of the San Francisco-based lawyers representing the group, said, "The main relief we are asking for is for the independent voters -- non-party preference or NPP -- to be able to vote for president on June 7 without tying up the voting lines and avoiding a situation of mass confusion.”

“We are asking the judge for an order that the poll workers be trained to inform voters that NPP voters have a separate presidential ballot rather than the voter having to ask for one, and that PSAs be sent out to all voters about how to vote NPP given the incorrect mandatory notices mailed out by government officials across the state, and to ensure that there are enough ballots for everyone to vote,” he told ABC News.

"We believe the City Attorney is confused about what the problems are: 50 percent of the NPP voters want to vote Democratic. As of May 24, only 14 percent of them have received their ballots. Half to 2/3 of the whole state votes by mail. Hundreds of thousands of votes at stake. The deadline to have the elections officials mail your ballot to you is May 31."

Sanders has not issued a statement on the matter.