I think that is related to a very important legal argument. Since multiple states do little or nothing to control their voter rolls, the result of any “popular vote” tally will necessarily include an unknowable number of illegal votes and duplicate votes, and thus be illegitimate. That is the stake in the heart of this Democrat scheme to thwart democracy. They know it will not stand up to legal scrutiny; it is an “insurance policy” to legitimize the real winner.
It’s a modern tragedy that we know it (NPV) is wrong, know a number of reasons why it is wrong and contrary to the spirit and best interests of the country, but can’t easily come up with a dead-nuts legal argument because the law is so complicated and built upon increasingly fine hair-splitting interpretation of precedent. And, those interpretations depend on a relatively small number of judges sworn to be impartial, whereas in fact, many of them are biased and political.
The logical solution for the national popular vote argument is that there must be an agreed-upon national standard to determine eligibility for a vote to be counted, to avoid disenfranchisement and protect the integrity of our elections. That would be fought by both sides and the NPV movement would wither on the vine as a result.
I have always advocated for a method of awarding electoral votes halfway between NPV and the electoral college; closer to reflecting the will of all the people and not automatically winner take all: by county. 3,242 counties in the US.
CA would not longer be automatically 55 EV for the libs, as the Inland Empire and Orange County would be finally be accounted for and truly represented. The large metropolitan centers in the largest states would not necessarily be dominant and lesser populated areas of states completely discounted.