In the 2020 presidential election, 158,407,383 votes were cast for presidential candidates. In the 2024 election, now that all votes have been counted, we can know that only 155,627,481 votes were cast for president. So the decline was 2,779,902 votes.
This is the first time that the number of votes cast for president has dropped since the pair of elections 2008-2012. Like 2024, 2012 also saw a drop compared to four years earlier.
Unfortunately, all election return data for United States presidential elections is flawed. That is because some states don’t report the number of write-in votes cast for candidates who hadn’t filed to have their write-ins counted.