I know someone (a Democrat) who had to rip her dead first husband’s page out of the voting book in Hudson County NJ, aftr repeated repeated requests to have it taken out. She could see signatures that he was voting, even though he was dead. The poll workers objected and she dared them to call the police. I’m sure it happens in some Republican strongholds, but I find it difficult to believe it happens with the machine precision that it happens in urban Democrat strongholds.
This is the single best arguement for the electorial college vs. popular vote. You might get a couple of disticts or state with vote fraud, but it takes a lot more effort to steal enough districts and state when using electorial college.