Projections of the winner in the US presidential elections are carried out using the official data offered by each state, through an internet portal.
It is a public portal that any citizen can access and make the accounts with which the experts elaborate the projection that determines who wins, by number of votes.
When it is determined that the advantage in a state is irreversible for a candidate, the electoral votes that each state gives are added.
When a candidate achieves 270 Electoral College votes, he is projected as president-elect.