I seldom delete a post, but my last post was so bad, I sent it to the trash.
Article II Section 1 clause 2 of the Constitution reads:
Each State shall appoint, in such Manner as the Legislature thereof may direct, a Number of Electors, equal to the whole Number of Senators and Representatives to which the State may be entitled in the Congress: but no Senator or Representative, or Person holding an Office of Trust or Profit under the United States, shall be appointed an Elector.
The whole winner-take-all election by state thing is merely an extra-constitutional state-level custom, and individual states could change it if they wanted to.
However, there would be a huge public outcry if the people’s votes were taken away by the state legislature, so I think that any change is highly unlikely.