Screenshots of the app the caused the Iowa caucus failures
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The job of an election isn't just to decide things, but to find agreeable consensus — so a decision has to be so clear, most people can accept it even if it goes against every fiber of their body. And this form of trust in the correctness of the process works much better with paper ballots than anything else, because large scale manipulation is extremely resource intensive to pull off without being seen and it is easier to trust fellow party members when they oversaw the process and didn't find manipulation, than it is to trust a few technical experts who sre unable to substancially check anything anyways, because they themselves have to trust so many things.
Electronic voting has only been around for a couple decades at best (and that's generous). It is definitely not hardened by time.
"It is best to wait. I got fooled."
They are rigging the primaries against Bernie just like they did in 2016.