OK, you got two big Constitutional constraints. One is the number of electors from each state:
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.
Constraint two is that at some point each elector must write the name of the one person they are voting for President on a piece of paper.
The Electors shall meet in their respective states and vote by ballot for President and Vice-President, one of whom, at least, shall not be an inhabitant of the same state with themselves; they shall name in their ballots the person voted for as President, and in distinct ballots the person voted for as Vice-President, and they shall make distinct lists of all persons voted for as President, and of all persons voted for as Vice-President, and of the number of votes for each, which lists they shall sign and certify, and transmit sealed to the seat of the government of the United States, directed to the President of the Senate;-The President of the Senate shall, in the presence of the Senate and House of Representatives, open all the certificates and the votes shall then be counted;-The person having the greatest Number of votes for President, shall be the President
If I understand correctly, you are saying that every state legislature can agree to participate in a plan to allocate electors from their state based on things that happen in other states?
Like, for example, my state may 21 electors and have a 50/50 vote which would cause me to send the score 10.5-10.5 to some algorithm that might, based on things that happened in other states, tell me to allocate the state's electors 13-8?
This may not literally offend the Constitution, though I suspect it might be challenged, but it still has the problem that for it to work you need all (or most) of the 50 states to sign up, which is statistically more difficult than just getting a Constitutional amendment.
I'm saying that every state delegate in the compact would be obligated to vote for the same person. So, if Texas and California sign on to this compact and Bob Bunghole wins through the point system, all delegates from both Texas and California would be obligated to vote for Bob Bunghole. It would be a winner take all for every state in the compact instead of a winner take all for a single state.
Well, that's a version of what I said. Texas and California agree to participate in System X. System X takes the election data from both states, runs it through an algorithm and the algorithm tells each Texas and California elector how to vote. (I think in your case is just that the algorithm is whomever gets the most popular votes in both states gets all the electors in both states.)
Again, to get all 50 states to agree to this would be harder than amending the Constitution to have a national popular vote.
You don't need all 50 states, you should need enough states to get 270 delegates. Also, you don't just have to exclude states that are not in the compact from the results tabulation. They could count other states plurality system as voters just approving a single candidate. I'd want to do whatever it takes to get rid of the state winner take all system. If that means red states having a little more voting power per person to get them to on board, then so be it.
Hmm, not sure a system that disenfranchises 49% of the people in the country will hold up, but I don't see how you're going to get it either.
Let's say I have California and New York signed up. Why would Texas vote to join?
It would get candidates to pay more attention to Texas and Republican voters from the blue states would also have more sway. It also wouldn't necessarily be just California and New York gaining control of Texas electoral votes. Even if other red states do not agree to the compact, you could still use their results in the tabulation process so it won't just be the blue states running roughshod.
It seems like it will perpetually be the case that the current system is perceived to be to the advantage of one side or the other. Thus, it will perpetually be a challenge to get the advantaged side to agree to participate in the system.