Gillum will now square off with DeSantis in what will be viewed as a referendum on Trump in a battle to replace Scott, who easily won his primary battle Tuesday for the Republican nomination to challenge Bill Nelson, a moderate Democrat, for his US senate seat.
The nomination is historic - Gillum is the state's first African-American nominee for governor.
He also dismissed the congratulatory tweet from progressive candidate Alexandria Ocasio-Cortez to Gillum, adding that there are people in Florida "who have fled socialist countries like Cuba and Venezuela" and that they don't want that "imported into Florida".
Gillum won the primary with 34 percent of the vote, the Associated Press projected Tuesday night with 87 percent of precincts reporting. Graham is being challenged by former Miami Beach Mayor Philip Levine, Tallahassee Mayor Andrew Gillum, billionaire Jeff Greene and Orlando-area businessman Chris King. Check back here for updates.
DeSantis sailed to victory in the Republican primary, defeating a longtime favorite of the GOP establishment with a campaign based largely around President Donald Trump.
Like Sanders, Gillum has kept his criticism of President Donald Trump at a relative low boil, instead focusing - while urging others to follow suit - on issues that could bring new voters out to the polls.
Gillum will face Republican gubernatorial candidate Ron DeSantis in November.
The conservative DeSantis easily won the Republican primary by highlighting his enthusiastic loyalty to Trump.
Gillum was the only candidate who said he'd raise corporate income taxes, and he often talked about winning a lawsuit against the National Rifle Association during his time as mayor. His grassroots campaign mirrors that of Ocasio-Cortez, whose takedown of New York City goliath Rep. Joe Crowley sent shockwaves through the Democratic Party earlier this year.
One of the first ads DeSantis ran for the race featured the candidate teaching his children how to say Trump campaign phrases and reading stories about the president at bed time. U.S. Sen. Bernie Sanders of Vermont endorsed him. Tonight, Floridians joined Andrew in standing up and demanding real change and showed our nation what is possible when we stand together.
DeSantis entered the race a month after Trump's December tweeted that he would make "a GREAT governor". Trump cheered DeSantis' victory on Twitter Tuesday night, writing: "Ron will be a fantastic Governor. No one person can take on the economic and political elites on their own", Sanders said in a statement.