There are also data points for Democratic Party overperformance. What does Democratic Party overperformance look like? Well, the 1st midterm of a new President is historically disastrous. This generally happens to both parties. The last two times the President's party gained seats in their first midterm election were 2002 (post 9/11) and 1934 (FDR coalition). Since World War II, the President's party has lost an average of 28 seats. Anything near a split Congress would be overperformance for the Democrats, historically speaking.
In 1991, I read a book called "Generations: A History to America's Future". It theorized a cycle to American history based on generational patterns. In 1991 this book predicted an American crisis sometime around 2020. I always found this book to be very compelling. Usually, the crisis is won by the younger generation imposing its will on the future of the country. This got me interested in the 1934 election (since it was pivotal in America's last crisis era) so I dug up and read a 1979 book called "The Creation of a Democratic Majority 1928 - 1936". That book showed how the FDR majority was the result of new voters (both younger and 2nd generation American that had not previously voted) and NOT the result of pre-existing voters changing sides. In other words, the FDR majority was the result of the younger generation defying the odds and the expectations and imposing its will on the future of the country.
One big difference between 2022 and 1934 is that older generations live longer and so have a bigger impact on the vote to prevent the future young Americans want to build for themselves. I don't know if 2022 will be a 1934 election. I certainly hope so but there are plenty of datapoints suggesting otherwise. Will be interesting to see what the young people do - I am rooting for them to live in the America they want for their future.