One thing that I have noticed looking back on recent years' electoral maps is the swing at the state level.
There is something that I noticed. In the past, states swung in different directions more than they do now. For example, the biggest swing towards Kerry was in Vermont, a small and socially liberal anti war state. It went 13% against the national popular swing. Then, in 2020, the biggest swing towards Trump was in Hawaii, which was only 5% against the national popular vote.
2016-2020 swing reversed for comparison purposes:
I chose 2000 to 2004 because the popular vote margin change nationally was similar. It provides a good demonstration. Bush pushed the entire lower Northeast towards his side (he still lost there), and the western US from Washington state to Minnesota moved against him.
Why is there significantly less deviation on the 2016 to 2020 swing map than 2000 to 2004 despite the 2000-2004 and 2016-2020 swings being similar?