Washington (CNN) Andrew Gillum, who won the Democratic primary for Florida governor in a stunning upset Tuesday, raised $1 million in the first 24 hours after his nomination, according to spokesperson Geoff Burgan.

Gillum, the mayor of Tallahassee, Fla., is Florida's first African-American major-party nominee for governor and is a progressive backed by independent Sen. Bernie Sanders of Vermont. He was the only leading Democrat in his primary to endorse "Medicare-for-all" single-payer health care, a top progressive agenda item and the policy most famously championed by Sanders.

An early underdog in a crowded field, the 39-year-old edged out former Rep. Gwen Graham to capture the gubernatorial nomination with the support of grass-roots Florida progressives.

He was also backed by a coalition of groups like the Collective PAC, which is dedicated to elevating African-American candidates; Indivisible, an organization formed in response to President Donald Trump's election in 2016; and the Working Families Party.