The Seventeenth Amendment has already brought us too close to that precipice. It should be repealed, along with the Sixteenth.
A “republican” form of government means that the voters do not make laws themselves but, instead, delegate the job to periodically elected officials (Congressmen, Senators, and the President). The United States has a “republican” form of government regardless of whether popular votes for presidential electors are tallied at the state-level (as has been the case in 48 states) or at district-level (as has been the case in Maine and Nebraska) or at 50-state-level (as under the National Popular Vote bill).