Moreover, Florida does not actually have runoff elections for gubernatorial races; DeSantis would only need a plurality of the vote to win.
Florida voters on Tuesday continued a two-decade streak of Republican dominance by electing former U.S. Rep. Ron DeSantis as governor.
Gilllum said he called DeSantis and congratulated him.
Had Gillum won, he would have been the first black governor of Florida.
DeSantis, 40, was considered an underdog before Trump tweeted his support for DeSantis in December, a month before he got into the race.
Gillum was favored by polls to win the state, thanks to his strong support from the African American community and young people.
"I think if Republicans vote and vote in big numbers on Tuesday, we will win all of these races", he said at a rally outside the Freedom Pharmacy on the east side of Orlando.
This year's totals far exceed those of 2014 midterms, but are still short of the 6.6 million who voted ahead of Election Day in 2016. On issues like climate change, which is increasingly important in Florida, Mr. DeSantis has said he didn't want to be known as an "alarmist", while Mr. Gillum promised to be a governor who "believes in science".
For the last few weeks, Real Clear Politics' average of the key polls has given Republicans 50 "safe" Senate seats and narrow leads in two of the seven "tossup" races (Missouri and Nevada). He enjoyed support from President Trump throughout his campaign.
In Colorado, Democrat Jared Polis was set to become the first openly gay man to be elected governor of a U.S. state, after NBC News projected him to win against Republican Walker Stapleton. Marco Rubio, R-Fla., state Rep. Matt Caldwell, the Republican candidate for agriculture commissioner, and Ashley Moody, a former judge who is the GOP nominee for attorney general. Fox News' Decision Desk still has projected that race as too close to call.
"My most significant and valued supporter is standing right next to me, despite what the media might say", DeSantis said of his wife Casey.
The race was the much-anticipated match-up of the ideological wings of each of the major political parties, with DeSantis representing the GOP base that backed Trump, Gillum representing the activist grassroots element of the Democratic Party.
Republicans said they cared most about immigration, then health care, then foreign policy.