Reposting a previous comment

There is no Constitutional provision or Federal law that requires electors to vote according to the results of the popular vote in their States.

For the non-yanks, when you tick the box next to "Genocide Joe", you aren't actually voting for him, you're voting for the people who pinky promise to do so but aren't actually required to.

Ordinary citizens are not allowed to cast votes for a presidential candidate. Only the electors, who will face no consequences aside from party disciplinary action should they break the “gentleman’s agreement”, have this power.