Regarding 1980, unless Bush's job approval rating suddenly drops about 15-20 points, there is exactly a zero percent chance of Bush replicating Carter's belly-flop in 1980. He could lose, but the end collapse is simply not in the cards. We could still see Kerry, however, reprise the Carter/Dukakis splat. I doubt it though. I am thinking a 50-80 electoral vote win is what we are looking at.
Hopefully, you will address the next to last poll query. In any event, the data points are too few, to have any statistical significance. Which proves the point, that the break theory has no traction - either way. It depends on the situation in detail, and that takes judgment. Speadsheets just won't cut it.