Holding a launch rally after the campaign effectively gets under way is hardly a new political play; President Obama announced his 2012 re-election bid more than a year before his first official rally, and early Democratic 2020 front-runner Joe Bidenheld his “kickoff rally” about a month after he entered the race.

Still, Mr. Trump has ushered in a new style of presidential politicking with his perpetual campaign mode. His predecessors waited well into their first terms before making their intentions known and avoided overt campaigning so early in the primary process.

At a recent event in Iowa, Mr. Trump suggested he hadn’t shifted fully into his campaign gear, declaring: “This isn’t political season quite for me. It’ll start next week.”

Mr. Trump and his team believe this is the right moment to re-assert his campaign prowess, as their operation has expanded and the Democratic primary field appears set. They selected the battleground state of Florida to stake their claim with one of the large-venue gatherings that defined the president’s 2016 operation.