"I find that the threat of a potential emergency is imminent", Scott said in a seven-page executive order.
Several protests are being planned in response to Spencer's speech on Thursday at Phillips Center for the Performing Arts at the University of Florida, which follows several other events in the past that sparked protests and counterprotests.
Spencer was to be a featured speaker at the August rally in Charlottesville, Virginia, at which one person died, but authorities stopped the event from taking place after protests and counterprotests turned violent.
The order allows state, county, and local agencies to coordinate their resources more quickly and freely before and during the rally in Gainesville and activates the Florida National Guard.
Officials at the University of Florida said they expect to spend about $500,000 on security Thursday. "I think that's the best way to look at it". After they threatened to sue, school officials said they would try to accommodate Spencer if he renewed his request for a different date.
Spencer, 39, is head of the National Policy Institute, which advocates for white people to maintain their European heritage and rejects racial equality and the value of diversity.
Spencer said Tuesday that the protests at Auburn and Texas A&M were limited to "some mild violence" because police did their jobs.
"Law enforcement is going to be well-prepared", Bondi said.
Scott's order came at the request of Alachua County Sheriff Sadie Darnell, who said she sought the emergency declaration "more so of being able to get the resources needed to prepare, rather than a sense of alarm regarding the protest".
"We're not even there yet, in Gainesville, at all and they're already enacting a state of emergency based on protesters already there", Padgett said.
Spencer may be best known for a controversial speech last November in which he mixed his white nationalist views with praise of Donald Trump's election win.
However, we have zero tolerance for violence and public safety is always our number one priority.
No campus group invited Spencer to speak, and the university is not hosting or sponsoring the event.
"We are hoping this is a nonevent", Darnell said. "Don't let the University of Florida be defined by Richard Spencer". "It is our creation and our inheritance, and it belongs to us", he said.