Which process is used for the indirect election of the U.S. president?

The process used for the indirect election of the U.S. president is the Electoral College. This system was established by the Founding Fathers in the Constitution and serves as a mechanism by which voters in each state cast their votes not directly for a candidate, but rather for a slate of electors pledged to that candidate. Each state has a certain number of electors based on its population and representation in Congress, and the candidate who receives the majority of the electoral votes (270 out of 538) wins the presidency.

This process was designed to balance the influence of populous states with less populous ones, encouraging candidates to campaign in a variety of states rather than focusing only on those with higher populations. Consequently, while citizens vote for their preferred presidential candidate, it is ultimately the electors chosen in each state who officially elect the president. This indirect system contrasts with direct popular voting methods, where every citizen's vote contributes directly to the outcome.

The other options, such as a national referendum or direct popular vote, would imply a different method of voting, which does not align with how the U.S. elects its president. A state assembly vote would involve the state legislature rather than the electorate, further differing from the constitutional process.