I'm preeeeeetty sure they could afford direct, un molested (maybe not if Republicans are around tho) copper wire to a kill switch. Reading resistance on the receiving end would ensure the line hasn't been tampered with.
It's only like technology over 100 years old but what do I know.
Just have a big "leader board" displaying everyone's votes. They can double-check that they voted how they meant to, and the votes are right there for everyone to see.
100 years isn't that long ago. It's only 2-3 generations from us. Hell, people in office of that generation are only now starting to die lol. We'll probably have to wait until gen x and millennials are running the show.
Myself, id prefer direct democracy; once automation frees up our time, allows ubi and education and medicine get recognized as an inherent human right. Since it's all a part of our global heritage.
So post capitalism.
And only then if we've unlocked the tech tree to allow socialism. No dice if we buy the authoritarian, neo-fuedalism expansion pack. If we buy that, then fuck it, just reset the game.