When did "Trump fatigue" start to become a factor for voters?

[pbrower2a]

The difference between 2016 and 2020 was demographics. Few people changed their minds, but new voters thought differently in 2020  from the old voters of 2016. About 1.6% of the electorate dies every year, almost entirely among people over 50. Silent, Boom, and early-wave X voters vote about 5% more R than D; voters under 40 vote about 20% more D than R. Over four years that is enough to swing the vote from a Trump win of the Electoral College to a Trump loss. That would have been enough for Trump to lose Michigan, Pennsylvania, Wisconsin, and Florida in 2020 if no other demographics applied. People loved Trump or hated him in 2016, and so it was in 2020 as well.

OK, Florida attracts elderly conservatives, and the Trump campaign had an effective Commie-baiting campaign to appeal to Cuban-Americans. So Trump lost Arizona, Georgia, and NE-02 instead, and that is a demographic wash and roughly the same effect in the Electoral College.

Going on an assumption of more of the same, nothing changes except for Biden winning North Carolina in 2024..