Mayor Wu won a ringing endorsement from the city’s largest public safety unions— the Boston Police Patrolmen Association (BPPA) and the association’s affiliated EMS partners— during a press conference held at the BPPA’s Dorchester headquarters on Thursday.

Union officials said it was the first time in 30 years that they have endorsed a sitting mayor for re-election. It comes as Wu is facing a potentially stiff challenge from Josh Kraft, the philanthropist, former non-profit leader and son of New England Patriots owner Robert Kraft.

Larry Calderone, the BPPA’s president, said the decision to back Wu was not a difficult one for the men and women who patrol the city’s streets each day. Calderone and his the BPPA-EMS union president Jason Yutkin credited Wu with bargaining fairly with their members and reaching a contract agreement in her first term and for making investments to add more Boston Police officers to the ranks through academy classes.

“I say that as strongly as I possibly can as we want her to be re-elected in November,” said Calderone, who says Wu has been a constant ally to his officers in moments of stress, injury, and insult over her time in office.

“Every time there's been an awful event, a tragedy, she's been there with us,” said Calderone. “She leads by example. She loves her police officers and she shows it. She values what we do every day of the year.”

In accepting the endorsement, Mayor Wu said she was honored and proud to receive the union’s nod.

“We are the safest major city in America because of your efforts, and we are intending to keep that going each and every day,” said Wu. “I am so grateful for the work that you all put in each and every day, and I know that we all feel there's a still a lot more work to do and that we're never going to be satisfied until we've eradicated violence in the city and any incident is one too many.”

Wu added that she was “very proud to sit across the table from these hard bargaining unions to know and to understand the details of what every word in those contracts means for your families at a time when there are so many who are looking to cut city services,” she said. To call for slashing budgets, whether it's public safety or city services in general, or trying to just paint a picture that city workers are, or public servants in general. And government is about fraud or waste or trying to maximize the efficiency. I want to hold up Boston as example of where we are getting the best bang for our buck. City workers are first responders, our teachers, our public works employees across the board. These are the people and family members who make our city run. And I will stand next to each and every one of you to continue putting the resources where we are serving the residents of Boston.”

In a poignant moment, Calderon called for a moment of silence for BPD Detective Mark Walsh, who was laid to rest on Thursday after a huge wake and funeral at St. Gregory’s Church in Dorchester. The 51-year-old father of-two and veteran police officer in districts across the city died after a brief illness prompted by influenza last week.

“Last night, hundreds of officers stood outside the church down at St. Greg's,” said Calderone. “We walked through, we paid our respects like we do all the time, but so did Mayor Wu, and I'm taking the opportunity to make sure that we say that here today because she stood at the altar with the Boston Police Commissioner, the command staff of the BPD and other officers and family members, and watched as every police officer, detective, guest, family and friend, made their respects to our fellow umbrella in the church.

He added: “This is who the mayor is. I want to let that sink in. It's the person that she is the human being that she is the leader of the city of Boston, that she has exuded and led by example every day.”

The union officials said the timing of the endorsement— just days before Mayor Wu will be called before a Republican-led Congressional committee that’s expected to grill her and others on public safety and immigration issues— was not related to the national political dynamics.

“It has nothing to do with the trip to Washington D.C.,” said Calderon. “Our goal here is to stress… that we want to see her reelected. She's been a great partner at the table. She's supportive of everything that the first responders and our two organizations have been doing. And we can't continue to provide these services, hire hundreds of police officers as she's been doing for the last few years.”

For her part, Wu said she had no idea that “the unions were going to take this up in the moment that they did.”

“It was a wonderful surprise to get a note from Larry and then to learn that both organizations had decided to weigh in and to weigh in strongly. And for that, I'm incredibly grateful. It reinforces the truth about our city and who we are.”