To sway an election, even a close one (e.g. PA or GA in 2020) you'd still need tens of thousands of votes.
The sheer scale of an operation to cast that many fraudulent ballots has such an infantessimally small chance of not being discovered (e.g. "Sir/Madam our records show you've already cast a ballot. You'll have to fill in this provisional one and come in with ID to verify")
The sheer scale of an operation to cast that many fraudulent ballots has such an infantessimally small chance of not being discovered (e.g. "Sir/Madam our records show you've already cast a ballot. You'll have to fill in this provisional one and come in with ID to verify")