I understand entirely. I've been studying this stuff closely ever since they stole the 2000 election.

The problem with rigging Congressional districts is that there are so many of them, all run by different people, in different regions of every state, that it becomes impossible to keep close enough track of them to 1) Pull off the crime, and them 2) Keep it quiet. With multiple people involved with each district, sooner or later you'll have someone feel guilty, get arrested and want to cut a deal, change their political affiliation, get angry and want revenge, etc. With that many people, in that many districts, it would be impossible to keep it under wraps.

Presidential elections are much easier. You only have to flip one race in only seven swing states, a much easier assignment.