Tallahassee Mayor Andrew Gillum became the first black Democratic gubernatorial candidate in Florida's history by defeating centrist former Rep. Gwen Graham. In this image, Beverly Putzke fills out her primary day voting ballot at a polling station in St. Augustine, Florida, Aug. 28, 2018 Joe Raedle/Getty Images

Tallahassee Mayor Andrew Gillum became the first black Democratic gubernatorial candidate in Florida's history on Tuesday by defeating centrist former Rep. Gwen Graham.

Gillum's win was most unexpected as he hadn't led in a single poll. He was backed by Vermont Sen. Bernie Sanders who drew more than 1,000 people to a rally in Tampa earlier this month. In a statement, Sanders said Gillium had "laid out a vision for a new course for the state of Florida and our country."

Gillium, 39, was born in Miami and was the first member in his family to graduate from college. Before becoming the mayor of Tallahassee, he became the youngest person in history to be elected to the Tallahassee City Commission.

He is a strong advocate of criminal justice reform. He had openly spoken about watching his brothers get arrested when they were young.

“Growing up…every one of my older brothers had some kind of criminal history. There were not a lot of opportunities to my brothers to go and work at some place. Our society doesn’t look well on people who have a criminal record. I believe firmly that people deserve second chances. You make mistakes, you break the law, you pay the penalty, but that you ought to be given a second chance,” he said in a video.

Gillium said he wants to address the issue of income inequality in Florida with his “Faire Share for Florida’s Future” plan which seeks the richest corporations to pay little more in taxes. The money will then be spent on educational needs, which include rebuilding public schools and starting vocational training to help people get more jobs, Heavy.com reported.

He is also a proponent of gun safety reform and has led several marches in the wake of Parkland shooting.

“Common sense gun safety policies including a ban on assault weapons, large capacity magazines, and bump stocks; strengthening and requiring universal background checks for all gun sales; closing private sale loopholes; restricting gun access for the mentally ill and known foreign and domestic terrorists; closing the ‘Boyfriend Loophole’ and prohibiting gun possession for those with felony and misdemeanor domestic violence and stalking convictions; and banning the purchase and possession of armor piercing bullets,” according to his website.

His site describes President Donald Trump’s Health Care Plan as “disastrous." As a governor, he promised to extend Medicaid to at least one million Floridians. Gillum said he “wants to protect and expand Floridians' access to quality, affordable healthcare, especially people with pre-existing conditions.”

He also promised to “make protecting the Everglades and Lake Okeechobee a priority, work to keep our water clean from toxic algae blooms, and fight to protect Florida’s access to clean water sources.”

Gillium will face Ron DeSantis, a Trump-endorsed Republican, in the general election in November. On Monday, Trump called DeSantis a "special person who has done an incredible job” and post the primary win Tuesday, he said DeSantis "will be a fantastic governor."