One. Increased diversity. These collar counties now have significant African-American and Hispanic populations voting heavily democratic, as opposed to being nearly White in the '80s and even part of the 90s.
did you not read the first three words of the title?
Two. Increased antipathy of college educated voters, especially those with postgraduate degrees, to a Republican Party platform that stands for square in favor of global warming being a hoax, a base that opposes teaching evolution, believes that homosexuality and transgenderism are mental illnesses, etc etc.
skeptical. It sounds like too much of a self serving story. The republican party was arguably worse in the 80s with like the schlafly and helms types.