2022: If 2021 races are counted, Virginia. Otherwise maybe Georgia.
2020: If 2019 races are counted, Kentucky. Otherwise Montana?
Both KY-GOV 2019 and VA-GOV 2022 were absolutely fascinating races. Both, IMO, demonstrated that tried-and-true tactics are never completely guaranteed to succeed.
For instance, the Republicans tried hard to make Beshear into a Berniecrat-goose-stepping-socialist, but they couldn't overcome the gross unpopularity of Mr. Bevin. (Also A.B. might be my politician-crush, but that's for another topic...)
And in VA circa 2021, Democrats employed the "tie-to-Trump" tactic, but it just wasn't enough to overcome Republican headwinds and a relatively poor campaign by McAuliffe.
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These two races really exemplify why I love gubernatorial races. Since governors, well, govern the state and are not involved with federal politics, this allows for so much more nuance. This nuance leads to a grab-bag of surprises, anti-trends, and other goodies.