How House Incumbents are Assigned After Redistricting
We are leaning on the FiveThirtyEight Redistricting Tracker for this: "Each representative is assigned to the new district that contains the greatest share of his or her current district. But if the representative has announced his or her intention to run for reelection in a different district ... we'll switch him or her over to that district instead."
FiveThirtyEight notes that some incumbents will switch districts if the partisan composition after redistricting has moved against them or to avoid facing another incumbent.
In some cases, redistricting will result in two representatives competing for a single seat. Initially, we will list both names. It could be two from the same party (e.g., WV-2), in which case a primary will eliminate one of them. In that scenario, we will remove the ousted representative from the list of incumbents.
Alternately, if there is one representative from each party (e.g., NC-11), and both win their respective primaries, they will meet in the general election. Where this happens, we will continue to list both.
Members not seeking reelection in 2022 will be listed if they are the only incumbent associated with a district. Announced departures can make it more palatable for the redistricting body to effectively eliminate their district or place the retiree in the same district as another incumbent, knowing there won't be a competition. These scenarios are more likely in states losing a district.
Some districts will not have an incumbent. There are several reason this will happen; the most obvious one is that the state has gained a seat in redistricting.