Anti-Catholicism as well as RN’s “experience” factor should explain much of 1960.
Imo Carter ran a poor campaign in 1976, with his victory map looking much like a regional one with wins in much of South and Northeast and not much else. Even in the South, Carter offended many of his fellow white evangelicals by agreeing to interview with Playboy and admitting to “lusting” after other women during his marriage
I recall reading somewhere that Carter led Ford in the polls by around 30 points in June 1976, around the time of the Democratic National Convention that year. And Carter's lead collapsed completely during the intervening months, and he only won by 2 points. Carter's collapse means that the Johnson landslide of 1964 will be the last sweeping Democratic landslide (in terms of counties carried) that we will ever see. If a Democrat wins a landslide victory again, it will probably resemble Obama's maps more than those of the past.
You would have made a prophetic analyst back in the 1920s, huh? People who are engaged enough in politics to post here shouldn’t use the words “ever” and “never” or “last.”
