APGP Federalist / Brutus / Electoral College Practice Test

The key idea is that the Constitution does not set a federal rule requiring electors to vote for the winner of their state’s popular vote or for any national poll. There is no constitutional or federal-law mandate that ties an elector’s vote to a specific outcome. States, however, can and do regulate electors: many have laws or pledges that bind electors to vote for the candidate who won the state's popular vote, and some penalties or remedies exist for faithless voting (the Supreme Court has allowed states to enforce such penalties). So while electors could in theory vote as they wish, there is a real system of state rules that commonly directs or constrains how they vote. This is why the best answer notes that there is no constitutional or federal requirement to follow the popular vote, though some states require it.