This shouldn't be a surprise: I think most HN members know that it's possible; we know that the rewards (incredible power, status, and everything you can get with them includig the spoils of office) are worth the investment (only $600K for this solution!); we know that there are many people, including politicians, unsavory enough to do it. The question is, why do we pretend it's not happening until there's a smoking…
1) Hacking voting machines to a significant extent would require a team of people, not just one guy, which dramatically increases the risk of exposure.
2) The reported vote count is usually very close to the predicted vote count, and always very close to exit polling results. The hacked results would need to be very close to the real results, or be combined with control over a huge number of people in the polling industry. Campaigns also run internal polls, so opponent campaigns might become suspicious if their own polls were not matching the results.
3) Recounts are possible and somewhat common. Therefore hacking could not be used to create a very close result that could trigger a recount, or it would need to be combined with actual ballot theft, or control over the officials doing the recount.
These are not theoretical concerns. See Bush v. Gore in Florida for what might happen if someone tried to hack a close election.
It seems to me that hacking an election would only be feasible in an already close race, would require the cooperation of a number of people with huge risks of exposure, and could still be caught by one of the many safeguards that exist.
Obviously I am only talking about hacking voting machines. It would not surprise me if the tactics in this article were common; using Twitter bots, spying on other campaigns, etc.