Florida, one of the key U.S. swing states, is used to electoral drama. A Florida recount battle that took more than a month of sparring — and a Supreme Court decision — famously decided the 2000 presidential election between George W. Bush and Al Gore.
Scott has already declared victory in this year's Senate race. As the contest tightened on Thursday, widely followed forecaster Nate Silver's FiveThirtyEight moved its rating on the Florida contest from "likely" Republican to "lean" Republican.
Silver pointed not only to Scott's dwindling lead, but also to reports of potential vote counting issues in Broward County, the state's second most populous county.
The Florida secretary of state's office did not immediately respond to CNBC's request to comment on reports of vote counting issues.
Prominent lawyer Marc Elias, who represents Nelson's campaign, said Thursday afternoon that he expected the margin in the race to narrow even more until a recount takes place. If the margin comes within 0.25 percentage point — where it stands currently — it would trigger a manual recount by hand.
Gillum's campaign has also started to prepare for the possibility of a recount, despite his earlier concession.
"Our campaign, along with our attorney Barry Richard, is monitoring the situation closely and is ready for any outcome, including a state-mandated recount," Gillum campaign spokeswoman Johanna Cervone said in a statement Thursday.
The Scott and DeSantis campaigns did not immediately respond to requests to comment on the possibility of a recount.