Requires either 50 states to change state law, or 3/4 of the states to ratify a federal constitutional amendment. And any of these requires the cooperation of the two parties to make it happen, or voting in their replacements. So it's a really tough nut to crack. It's hard to change the constitution. If 85% of the country had any damn idea how the current system works let alone a modern alternative, it would be straight forward but they don't. And any states that think they will lose their inflated advantage will refuse to cooperate.