Hillary Clinton campaigns in San Diego on Thursday. (Melina Mara/The Washington Post).

The gun violence prevention group with ties to former New York mayor Michael Bloomberg is endorsing Hillary Clinton for president on Friday, arguing that she is the most likely candidate to take action to toughen the nation's gun laws.

Everytown for Gun Safety, which includes Moms Demand Action for Gun Sense in America and the Everytown Survivor Network, joins a number of other gun-control groups and prominent advocates like former congresswoman Gabrielle Giffords in supporting Clinton over her rival for the Democratic nomination, Sen. Bernie Sanders of Vermont.

Bloomberg founded and bankrolled Mayors Against Illegal Guns, which in 2014 morphed into Everytown, an umbrella group run by some of his former aides. But despite Friday's endorsement, the former mayor has not announced a personal endorsement in the presidential race. He considered entering the race himself as an independent, but ruled out a run this spring.

Everytown's endorsement comes nearly two weeks after the National Rifle Association formally endorsed Donald Trump at its annual convention in Louisville, Ky., where the presumptive Republican nominee vowed to protect and expand gun rights.

Shannon Watts, founder of Moms Demand Action for Gun Sense in America, said in an interview that her group's leaders, who met with both Clinton and Sanders, were drawn to Clinton because she has prioritized gun safety in her campaign agenda.

“We’ve been watching this unfold and it has become clear that there really is only one candidate for president who has consistently supported criminal background checks for every form of gun sale," Watts said. "She has stood with survivors of gun violence, she has stood with mothers and women and all Americans who think this is one of the most important voting issues of this election."

Referencing Trump's campaign theme, Watts added, "Donald Trump is working to make America great again, but we believe Hillary Clinton is working to make America safe again, and that’s why we’re with her.”

John Feinblatt, Everytown's president and a former top adviser to Bloomberg at City Hall, said in a statement that Clinton is a "champion" for what he called "gun sense voters."

"Our litmus test is simple: does a candidate side with the public or with the gun lobby?" Feinblatt said. "Hillary Clinton passes that test with flying colors -- pushing back against the NRA's extreme 'guns for everyone, everywhere' agenda, and ushering in a new political calculus that saving lives from gun violence is a winning issue."

The endorsement comes a day after National Gun Violence Awareness Day, when Americans showed their support for the movement by wearing orange. In San Diego on Thursday, Clinton wore an orange blouse under her navy pantsuit while delivering her foreign affairs speech eviscerating Trump. Sanders, who also was campaigning in California, did not wear orange.

During the primaries, Clinton has used the issue of gun control to position herself to Sanders's left. Sanders has a mixed voting record on gun issues, which he defends by noting he represents a rural state with a rich hunting tradition.

Although Everytown does not mention Sanders in its official endorsement announcement, Watts said in the interview, "Senator Sanders does not have as strong of a record and does not seem to have as clear and passionate a commitment to this issue."