I'm doing some personal research on the electoral college as it has been becoming more and more relevant in modern US elections. I've seen tons of people talking about how it was designed to protect small or slave states, however when examining James Madison's notes from September 4th, the day it was debated, all of the discussion seemed to be over how it protects from total control by the legislature and corruption. I was wondering if there was a primary source to look at that would explain somewhat the reasoning behind giving each state the same number of electors as senators and representatives combined, as that seems to be something already decided on by the first time it is proposed. I am by no means a constitutional scholar and have not read the full text of Madison's notes as of yet, so I may have overlooked an obvious answer.
Just to clarify, I am not looking for someone explaining that the electoral college was put in place because of difficulty taking a true popular vote, or to protect the people against ignorance, nor am I looking for someone to explain the three-fifths compromise. I am looking for an explanation as to why the number of electors is not directly tied to the population of the state.