Major campaign underway to nullify Electoral College

[Nichlemn]

I think this underscores the real motivation for legislative action - which party stands to gain by NPVIC. The GOP had a clear structural advantage in the EC for a long time such that no non-Southern Dem won the presidency after Kennedy until Obama.

That's not evidence of a structural advantage: counting Gore as a southern Democrat, no non-southern Dem won the popular vote after Kennedy until Obama. No non-right-handed Republican won the presidency after Nixon until Bush Jr. - it's a structural advantage! Or, maybe, coincidence, or the way these things work.

You reversed my two clauses and their dependency. The structural advantage is measured by how the EC would go if the vote shifted to an even split between the two candidates. Until the last decade that advantage was typically for the GOP and an even race would be expected to go for the GOP. Since a big piece of that base since 1960 was in the South, a southern candidate could swing regional votes and get a win like Carter did in 1976. Gore was not really considered a Southern candidate after his 8 years as VP.

No, there wasn't. From 1960 to 2004, Republicans had the theoretical EC edge six times (1968, 1976, 1984, 1988, 1992 and 2000) while Democrats had it the other six times (1960, 1964, 1972, 1980, 1996, 2004). There appears to be no consistent pattern in the EC advantage.

[Nichlemn]

Is Bush 2000 the only reason it's only Democratic states signing on? Or is there some kind of status quo conservatism involved?

In theory, it shouldn't be too hard to sell to Texas, if you focused on it being the second-largest state but ignored by Presidential campaigns, and maybe tried a "Democrats have a structural advantage in the Electoral College now" argument, even though that's not true.