Bob, a 43 state landslide IS possible. 
Had John Edwards gotten the nomination in 2008, and the cheating scandal leaked a few weeks before the election, without time for the Dems to nominate a new candidate, I think a landslide of this sort would be possible. The same thing could happen now,if one of the candidates has a nasty scandal right before the election. Something like a racist remark in private or similar.
I doubt an Edwards cheating scandal would allow the Republicans to wrest that many blue states away from the Dems. And if Edwards’ opponent was McCain, McCain was not and is not a particularly appealing candidate.
Maybe a narrow Republican win, but not beyond that.
A landslide would happen any time one party nominates a candidate considered too radical by the middle of the voting public, probably combined with a revelation of that radical committing some wrongful act.
I’m not naming any names or parties since it could happen to either party.
1972 and 1984 were landslides without catastrophic events. (Or scandals, for that matter.)
Add me to the camp of: yes, it will happen again, who knows when, and who knows which party it will be.
If that’s true, great, and I would substitute WY. I didn’t think MT was potentially in reach for any Dem. If I’m wrong, hooray.
11, 11, and 11 votes in the poll. My inner mathematician is happy.