The compact does absolutely nothing to suppress a states vote. What an asinine assertion.
Since when?
Because the state's voters directly, or through the state legislators they elect, determine how their state's EV's are allocated. So, assuming a state votes popularly for a candidate who doesn't win the national popular vote, the citizens of that state are free to change the way it's EVs are counted in future elections. Other states cannot have any power over how the voters of any state decide to count it's votes.
A politician would have to campaign very differently if the presidency was determined by popular vote. Presidential candidates would completely ignore the rural states.
So this compact violates the intention of the electoral college, and I therefore do not believe the Supreme Court would abide it.
This is an attempt to circumvent the EC without a constitutional amendment.