Mr Bloomberg’s late stage infusion of cash reflects Democrats’ concerns about the tight race in a state that is a priority for President Donald Trump.
A victory for Mr Biden in Florida, the largest of the perennial battleground states, would significantly complicate Mr Trump’s path to reaching the 270 Electoral College votes needed to secure a second term.
Republicans, however, feel confident in their chances in the state, pointing to GOP wins in 2018 and stronger than expected turnout in 2016 as evidence the state is trending in their direction.
They have invested millions in Florida, focused on Latino outreach and boosting their field operation, and the state’s size and diversity makes campaigns there expensive.
In a sign the planned investment put Mr Trump on alert, the president tweeted out his disdain for Mr Bloomberg on Sunday morning, referencing the attacks the businessman received at a Democratic primary debate in February from Massachusetts Senator Elizabeth Warren.
He tweeted: “I thought Mini Mike was through with Democrat politics after spending almost 2 Billion Dollars, and then giving the worst and most inept Debate Performance in the history of Presidential Politics. Pocahontas ended his political career on first question, OVER! Save NYC instead.”
Billionaire Mr Bloomberg launched his own campaign for the Democratic nomination late last year amid worries about Mr Biden’s strengths.
Despite spending one billion dollars (£772 million) on his campaign, Mr Bloomberg struggled and dropped out in March, quickly endorsing Mr Biden.
One of the world’s wealthiest men with a net worth estimated to exceed 60 billion dollars (£46.3 billion), Mr Bloomberg exited the presidential race pledging to spend “whatever it takes” to defeat Mr Trump.
He has already invested millions to support Democrats up and down the ballot.
Mr Bloomberg transferred 18 million dollars (£13.9 million) from his presidential campaign to the Democratic National Committee and transferred its offices in six key swing states to the local Democratic parties there.
The businessman has contributed 500,000 dollars (£386,000) to Voto Latino to help register Latino voters, two million dollars (£1.5 million) to the group Collective Future to help register African American voters and two million to Swing Left, a group focused on electing Democrats in swing districts.
One of the groups he has founded and funds, Everytown for Gun Safety, has committed to spending 60 million dollars (£46.3 million) on elections this cycle, while Mr Bloomberg himself has pledged another 60 million dollars to support Democrats in House races.
His new spending is intended to boost Mr Biden before the start of early voting in Florida, which begins on September 24.
An adviser for Mr Bloomberg said much of the money will go to television and digital advertising.
Republicans are outspending Democrats by about eight million dollars (£6.2 million) in the state in future television ad reservations, according to a review of Kantar/CMAG data by The Associated Press.
