https://www.scientificamerican.com/article/presidential-debates-have-shockingly-little-effect-on-election-outcomes/

The first 2020 presidential debate did not go well for Donald Trump. Viewers were turned off by the president’s constant hectoring of Joe Biden. And many were alarmed when he not only declined to denounce white supremacists but went so far as to tell a far-right neofascist group to “stand by.” Polling by FiveThirtyEight revealed that 50 percent of people who watched the event rated Trump’s performance as “very poor.”

But while Biden clearly won the debate, this does not mean he will win the election. Studies indicate that televised presidential debates have very little, if any, impact on votes. For a variety of reasons, this observation is especially true in 2020.