What are the factors shaping voters’ choices in the US midterms 2022?

In the past, midterm elections have been kind of predictable. The president is slightly unpopular, his party loses some seats and most voters disappear for two years until they turn up in greater numbers for the main show. It’s been a pretty consistent pattern; since 1934, the president’s party has lost in almost every single midterm election, gaining House seats just three times and Senate seats in only six of the 22 midterm votes.

This year might not buck any of those long-term trends. The Democratic president Joe Biden has watched...