"I was able to show that you can be a reformer and you can also be pro-public safety," said Gascón.
The Cuban immigrant arrived in southeast Los Angeles County as a teen in the 1960s. After serving the military, he joined the Los Angeles Police Department, eventually ascending to an assistant chief position.
He earned a law degree and led the Mesa Police Department in Arizona. Then he returned to California where he led the San Francisco police department, and later co-authored Proposition 47, which reclassified some nonviolent felonies to misdemeanors. He credits the measure with reducing the racial disparities in drug offense prosecutions.
Many critics say it caused crime to increase in some communities.
Gascón argues in San Francisco, that was not the case.
"Overall the thing that I'm most proud of is that we have been able to show that you can lower incarceration and you lower crime at the same time," he said.
Under his watch, San Francisco did lead the nation in property crime. Gascón said most of those crimes were auto burglaries which did not change under Prop. 47, and dropped by 20% in the last two years.
Like the incumbent in the race, he's also come under fire over deadly police shootings.
"There is no question that we have problems with the law, and I have been an outspoken critic of the law, and even in cases where I was not able to move forward with a prosecution, when I found the use of force to be unnecessary, I said so publicly," he said.
Gascón said like in San Francisco, he would create an independent investigation bureau for police use-of-force cases, not seek the death penalty, and incorporate more science and data-driven technology.
"Artificial intelligence to remove race and race proxies from police reports before a prosecutor makes a prosecutorial decision to try to deal with the impact of implicit bias in our work."
The Los Angeles Times, U.S. Sen. Kamala Harris and former LAPD Chief Charlie Beck have endorsed Gascón.