“If the whole idea is that the national popular vote is fairly counted, it’s hard unless there’s buy-in by the counters everywhere, including in red states.”

Expecting Republican states to bypass a system that favors them is asinine. It's already only going to reach 270 if enough swing states join, some of which would selfishly prefer it if more attention were paid per capita to their citizens and issues during presidential elections, the exact opposite of what a fair and proportional representative democracy should be.

The least glitchy version is the one I imagined in 2001. My specific proposal involves a lot of interstate uniformity, and using an independent bipartisan mechanism. But it means going back to square one in each of the states.

That's far less likely to occur than even a constitutional amendment. Again, the problem is that using the popular vote is not a bipartisan issue; not only is the Electoral College designed to boost states with small populations, favoring Republicans, but many of those same Republican states intentionally suppress voter participation by various means to diminish the importance of the popular vote.