Few observers of US politics will be surprised to hear that recent opinion polls show a tightening presidential race in Florida.

This crucial swing state is used to dramatic electoral disputes, a result of its extreme political polarisation.

With the Florida vote often divided almost exactly in half between Democrats and Republicans, election outcomes may depend on small variations of support for either candidate among the multiple groups of the state’s vast and diverse electorate.

This year, three of these groups are attracting particular attention. Voting patterns among Cuban-Americans, senior citizens and former felons could well define who wins in Florida, and have an outsized influence on deciding who will be in the White House next year.

  1. Trump advances with Miami Cubans
    Many residents of Miami, Florida’s largest metropolitan area, will have noticed a recent uptick in the number of Spanish-language ads from Joe Biden’s campaign showing up in their computer or TV screens.

The barrage of Democratic ads is part of a late-game push to win Hispanic votes in this part of the state. But to some observers, this effort comes across as too little, too late.

“This is something the Democrats should have been doing months and years ago, not days ago”, Miami pollster and Democratic strategist Fernand Amandi tells the BBC.

Kamala Harris courts the Hispanic vote at a restaurant in Doral, Florida
A survey published in early September by his company, Bendixen & Amandi, shows President Donald Trump’s campaign making inroads among citizens of Cuban heritage, who make up around one third of Miami-Dade county’s population.

According to the poll, 68% of Cuban Americans in Miami say they would vote in 2020 for the president and only 30% for Biden. In 2012, nearly half of their votes had gone for Barack Obama, and in 2016, 41% of them voted for Hillary Clinton.

On Tuesday, Biden visited the Puerto Rican enclave of Kissimmee, near Orlando, promising economic aid for the Caribbean island and even playing a crowd-pleasing few seconds of Puerto Rican singer Luis Fonsi’s global mega-hit Despacito.

Polls still show an overall Biden advantage in Miami-Dade county. The Bendixen-Amandi survey presents him as being ahead of Trump by 55% to 38%.

But Amandi points out that Biden can’t afford to just win in Miami. He needs to win big. A narrow margin in favour of Biden here means Trump would need a smaller advantage in the rural and overwhelmingly Republican north of the state to obtain an overall victory in Florida. So conceding even some Miami Latino votes in Miami can become a big problem for Biden.