The New York Times used swooping arrows to show vote swings left and right for the 2016, 2020, and 2024 elections. A shift left makes the section of an arrow blue, and a shift right makes a section of the arrow red. They show these arrows for demographic groups, too, which have static sizes, but the map above scales the arrows for electoral votes.
I was trying to figure out where I saw this method before. Then I saw it:
More specifically, the wordless version:
Then I had to eat lunch.
