I’m not an expert in elections security, and so I leave it to others to tell me how vulnerable our systems really are. But the perception that our political systems are hackable is up since 2016, especially among Democrats. Republicans have long had concerns about “voter fraud,” and Democrats now have deep concerns about “hacking.” And one thing is almost certain: The Russian troll bots will be doing their darnedest to stoke these concerns as we get closer to November.
It would only take a few choice security breaches or even credible allegations of such breaches to upset confidence in the entire election if things are close. Like a single terrorist attack putting an entire nation on edge, If some fishy activity shows up in a few close elections, it could easily lead to a perception that wider results shouldn’t be trusted. This could trigger contested and bitter recount and certification fights.
If control of Congress hangs in the balance, this could get very ugly. Given the high stakes (if Democrats control the House, oversight of the Trump administration will change dramatically, and the chances of impeachment increase dramatically), political actors on the losing side will have a powerful motivation — and likely lots of external pressure — to challenge any suspicious results. And the public will be primed to be suspicious already.