Between 1952 and 2004 Virginia was reliably Republican. It had last gone Democratic in a close election in 1948. It never went for Carter even though every other former-Confederate State did so in 1976. It never went for Clinton in two near-blowout elections for him.
States can shift swiftly.
Parties change more than states and states like Alaska really don't change. Virginia was reliably red but was never in the safe column. It would be solid when we won and likely when we lost.
There's more going on then just parties changing. Nixon beat McGovern by 26 points in Vermont. I think it's pretty clear that if there was a 1972 do over, even without hindsight, Vermont would vote McGovern today.
The states can change if people move in, and if a state like Oklahoma were to receive a massive influx of urban voters from the West Coast and the Northeast it too would change. Just look at Virginia.
Most significant is that the sorts of people who voted for George Wallace in 1968 have gone from fitting the New Deal mode to fitting the right wing of the Republican Party -- just as the Eisenhower-Rockefeller voters began to go Democratic as the Republican Party neglected them. The RINO types that the Hard Right had castigated have gone where they are welcome. But whether moderates like Lloyd Bentsen and Al Gore could win in Texas and Tennessee is much in doubt.