Why are Florida and Pennsylvania so important to the 2020 US election?

Firstly, you have to remember that the overall popular vote doesn’t decide who becomes president.

The Electoral College votes does - and the first candidate to reach 270 Electoral College votes wins the election

FLORIDA or the ‘SUNSHINE STATE’

At this point of the race to White House, the most intense attention was on the swing state of Florida and the 29 Electoral College votes it has to offer (which is a lot)
Florida is also Trump’s home state, which he declared last year.
Florida has historically been a hotly contested state, with support for both Republican and Democrats finely balanced.
Most famously in 2000, Republican George W. Bush won Florida by such a close margin (just 537 votes) out of a total of six million votes cast
Because of such a small margin, the state law required a recount of votes which led to a month-long legal battle (the outcome of the 2000 elections was not known for more than a month after polling)
The battle culminated in a controversial Supreme Court 5-4 decision which effectively awarded Florida’s 259 electoral votes to Bush, even though Gore had won the popular vote by 543,895 votes. Again, it is winning the Electoral College that counts.
Florida was closely contested again in 2012 (Barack Obama vs Mitt Romney) and 2016 (Trump vs Clinton) with just about one percentage point separating the candidates.

PENNSYLVANIA or the ‘KEYSTONE STATE’

Pennsylvania is also referred to by most experts as the ‘make or break’ for the presidential candidate.
It means that a candidate may carry enough electoral votes to get to the 270 magic number if he wins Pennsylvania, which offers 20 electoral votes.
In 2016, Trump won Pennsylvania by a mere 44,292 votes, or 0.7 percentage point, over Clinton.
It was a huge win for Trump because no Republican has won Pennsylvania since George H.W. Bush in 1988.
Both Florida and Pennsylvania are considered must-wins for Mr Trump if he is to be re-elected to a second term.