As a preface, I do not have enough information from the article to form a strong opinion on whether or not any misconduct or alteration occurred with the vote, so attempting to comment in a non-partisan fashion.

But to respond to your post, I don't actually think that based on the premise of the article and the accusation that exceptional foresight is really necessary on the part of potential hackers/manipulators like you're suggesting. There is ample historical data for virtually every county in the United States as to which way the vote will go, and once the dataset is loaded, it would be pretty trivial to figure out which districts need someone to press on the scale a little in favor of one side or another. State-wide, certain states have swung back and forth from red to blue, but county to county, the changes are much more predictable. Combine this that you're looking at a handful of states and not nation wide, and it seems a bit more possible.

I want to reiterate I'm not making an accusation, but assuming there was a mechanism that "hackers" could use to influence the results, the scope and foresight necessary is easily attainable in common datasets online, with historical data going back pretty far.