“Nobody does that.”
They kinda do. Maybe not Groucho Marx disguises, but with phony docs of recently-deceased people, etc. I believe there was a time when Democrats would pile losers into vans and/or buses and shuttle them from polling place to polling place in exchange for money or goodies.
But you’re right; in this era, tweaking technology will be their method of choice.
However, these machines present a real risk.