#3 Doesn't require a Constitutiuon Amendment -- Electors are designated at the state level. So a state can choose to split up their electors proportionally based on the percentage of vote for each candidate.

Dropping the EC altogether or requiring states to proportionalize their EC reps would require an Amendment, though. That would require states to give up much of their control over the election process and create a national voter's registry, and getting the states to ratify an amendment that sharply decreases their power would be politically impossible for now.

Personally, I favor a national instant-runoff election -- one of the few cases where I don't support state's rights. It's the president, after all, it SHOULD be a National Election of all the citizens.