Meanwhile, the current governor of the state, Republican Rick Scott, has beat Senator Bill Nelson in the race for US Senate. Mr Scott beat Mr Nelson narrowly after an expensive race that ranks as one of the most expensive in US electoral history.
Mr Gillum called Mr DeSantis to concede, but vowed to continue to fight for causes he believes in.
In down ballot races, Democrats flipped two House seats from Republicans, with Democrats Debbie Mucarsel-Powell and Donna Shalala now set to become US representatives in January.
The Republican victory in the Florida Senate race reflects a broader trend for the GOP in that legislative body, as President Donald Trump’s party expanded its control there. The party flipped at last three seats from Democrats.
But, Democrats saw victories in ways that will hobble the president’s next two years in office, and gained control of the House of Representatives. Democrats will now yield power over congressional investigations, and will have the ability to re-open or expand investigations into Russia’s involvement in the 2016 election and any connection that involvement may have had to Mr Trump’s campaign.
Democrats also saw important wins in governors races across the country, even if Mr Gillum was unable to flip control in Tallahassee. As election results poured in from across the country, Democrats picked up at least six governorships from Republican hands. That means that the party will control at least 21 governor's mansions. Republicans, with four seats left to be decided on Wednesday morning, had retained control of 25 seats.
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