I was on a quest to find counties that voted for candidates that were blown out/lost, and yet, have voted for the opposing party of that candidate since. I found a few for John Kerry, Al Gore (largely in the South) and Michael Dukakis (a few in Iowa), but I am trying to find at least one for Walter Mondale. Does anyone know of at least one?
Colbert, Jackson, and Lawrence Counties in North Alabama would fit into the category which you seek. Mondale won these counties over Reagan 52-45%, 52-46%, and 51-47%. Thirty-two years later, Trump crushed Hillary Clinton in these counties, 67-29%, 79-18%, and 73-24% respectively. These three counties were once New Deal Democratic strongholds. During the 1960s and early 1970s, they temporarily broke away from Democrats.
In 1964, for example, they were among the counties that did not vote for Barry Goldwater; in 1968, they voted by landslide margins for native son George Wallace; and in 1972, they went by landslides for Richard Nixon over George McGovern. Jimmy Carter gained them back in 1976, and they did not vote Republican again until George W. Bush won them against John Kerry in 2004. Since then, they have become as Republican as the rest of rural Alabama.