Let me drill down to Texas, where I am quite active. I have been privy to a conversation[1] with Governor Abbot where he described in detail his horse-trading to swap precincts between Congressional representatives in order to: (1) maximize the number of GOP seats; and, (2) ensure the 'safety' of the win of preferred US reps. Secondary goals include trying to pass (Texas) constitutional amendments to make the following things illegal in Texas: any voting system that's not first-past-the-post; at large proposition mechanisms; independent citizens redistricting committees; etc.
[1] This occurred while I waited in line to vote.