Biden consistently held narrow leads in public polls throughout the fall, but neither side expected anything but a tight race in Florida after Trump beat Hillary Clinton in 2016 by 113,000 votes — just 1 percentage point. In the past decade, Florida has seen three governors' races, a Senate race and two presidential campaigns all ended with margins of 1.2 points or less.

The coronavirus pandemic fueled dueling campaign strategies, with Trump and Republicans continuing to execute a strategy of traditional door knocking and voter contact. Biden and Democrats pulled back those efforts amid the global pandemic. That change resulted in Republicans narrowing Democrats’ long-running registration advantage to just 134,000, which is the closest margin in recent memory.

Trump also reversed recent Democratic gains with Cuban voters, a large constituency in South Florida that he combined with overwhelming strength among white people, especially those without college degrees. Biden, meanwhile, cut into the traditional GOP edge with seniors, whose enthusiasm for Trump was sapped by the pandemic and other turbulence over the past four years.

There was also a major, Trump-driven turnaround in the way Florida voters cast their ballots in 2020. Republicans built and perfected mail voting in Florida over the past decade, and they generally win the mail vote in the senior-heavy state. But Trump’s persistent and unfounded claims that mail voting is tainted by massive fraud shifted how Republicans voted, with many opting for in-person voting this year.

The same shift happened everywhere in the country, but it was particularly notable in Florida given the state GOP’s experience with turning out its voters through the mail. It meant the Republican Party of Florida had to completely change up its election strategy, and Democrats assembled a huge advantage in mail voting that Republicans eroded once in-person voting began.