John "Jack" O'Neill has a baby face that gives away his status as the youngest of seven candidates running for the Democratic nomination for Philadelphia district attorney in the May 16 primary.

But O'Neill, 35, is quick to dismiss any implication that he may not be seasoned enough to take over an office with a $53 million budget and 600 employees.

"I am a lot more experienced and I do have a lot more knowledge about the office than anyone else," O'Neill, an assistant district attorney for 10 years before deciding to run for the top job, said in a recent interview.

O'Neill has garnered support from several local building trade unions -- sprinkler fitters,  ironworkers and plumbers, among others -- flush with cash to spend on their chosen candidates. In a Democratic primary race with no incumbent and little name recognition among the candidates, that backing can count for a lot because the unions can help pay for mailers, and radio and television advertisements.

A political action committee started by Local 98 of the International Brotherhood of Electrical Workers and other building trades unions has spent $144,340 for ads in support of O'Neill. The PAC, Building a Better Pennsylvania, backed Jim Kenney's successful run for mayor in 2015. A few days later, a coalition of politicians from the city's Northeast, including U.S. Rep. Brendan F. Boyle, City Councilman Bobby Henon, and City Controller Alan Butkovitz, endorsed him.

O'Neill, who talks with the excitement of an eager new-to-politics candidate, has embraced the idea of the labor unions working closely with the District Attorney's Office. He called the relationship "essential" to the next district attorney's "ability to do his job."

"They provide skilled jobs where you can get a job quickly. One of the things that is missing right now. … A lot of people don't have the time to go get a [community college] degree and then start making money," he said, referring to diversionary programs that send defendants to community college. "A lot of people who are being prosecuted have children, have bills, and they need a check now. Skilled labor can get you a check a lot faster than a degree can."

O'Neill has vowed to create a deputy of labor liaison position within his office if he becomes the next district attorney.

"Good-paying jobs need someone supporting them," he said, following a big endorsement rally at the Plumbers Union Local 690 Hall in Northeast Philadelphia in late April. "When you have situations, for example, when someone illegally classifies a job the wrong way so that they can rip off their workers … it only makes sense to have a DA's Office that supports the law. That's the job of the DA's Office."

As for questions about giving the unions getting special treatment, O'Neill said he has not given any special treatment to anyone  in his 10 years working in the District Attorney's Office and would not as head of the office.

O'Neill grew up in Chestnut Hill, attending Masterman in Center City for Middle School and Chestnut Hill Academy for high school.  He said he "always wanted to be a DA."

"I think going to Masterman and having friends in every neighborhood in this city and seeing these incredible smart kids, some much smarter than me, seeing what they had to go through every day, I think all those things culminated in me just having a strong, strong drive toward  public service," he said.

He went on to major in political science and history at Rutgers University in New Brunswick and went on Florida State University for law school.

After law school, O'Neill landed a job as an assistant district attorney in Philadelphia, prosecuting domestic violence cases. About a year later, he was promoted to the juvenile unit, where he handled child sexual assault cases.

When he joined the office, he worked under the leadership of Lynne Abraham, whom he said he admired. O'Neill was there for the rise and fall of the current district attorney, Seth Williams, who faces federal charges, accused of selling influence in exchange for gifts. O'Neill rose through the ranks and joined the homicide unit.

"What I loved about Seth is that he was a real reformer,"O'Neill said. "The reality is he had a lot of good ideas and he also created a culture in the DA's Office in which if you had a good idea or if you had something you thought was better, he would listen to you and he would support the programs."

When the initial reports came out accusing Williams of not reporting gifts, O'Neill said he was disappointed. The indictment, he said, was "shocking."

"I think a lot of us who were in that young generation of progressive, liberal reformers who saw him as our, like, Bobby Kennedy, our guy who was going to lead us into this, felt betrayed by that and disappointed," O'Neill said. He is the only one of the eight candidates (sevens Democrats and one Republican) who  worked under Williams from the beginning of the DA's  tenure.

O'Neill said he would like to expand several diversionary programs started under Williams' leadership and to introduce others such as bail reform and detainer reform. He added: "It wouldn't be status quo at all."

"A lot of those diversionary programs are only reaching a small percentage of the people who are eligible for them," he said.

O'Neill, like most of the candidates, says he wants to create a system in which people who are in jail for low-level, nonviolent offenses are not stuck there simply because they cannot make bail.  O'Neill wants to be able to release such people to drug or mental health treatment or a job training program. He says those programs reduce recidivism.

He says he would also like to allow people arrested for a second offense while on probation for a minor offense to be sent to drug treatment programs when appropriate and not sent back to jail. That practice is a "detainer," he said.

"It's a waste of money, it's a waste of resources," O'Neill said.

And then there is the idea of trade unions helping the system by providing jobs to those in diversionary programs or coming out of prison.

During his endorsement rally, O'Neill called the local labor unions "the best job creators." The labor leaders at that April rally didn't get into the specifics of their endorsement.

Wayne Miller, business manager of the Sprinklerfitters Local 696 and president of the Philadelphia Building Trades Council, told the crowd of a few hundred: "Sometimes people have it and you just don't know what it is, but Jack has it."