To assume that it refers to voters choosing Electors is to negate the power of legislatures to choose the method of selecting Electors, because it already jumps to citizen popular voting as the method.
-PJ
The point is that we have an Election Day for the popular vote. Election Day is singular, not election days or weeks.
Anything other than Election Day compromises the integrity of the vote, delays the tabulation, and opens the window for large scale voter fraud.