One of the biggest culprits is ‘early voting’. That gives the opposition (usually Dems) an opportunity to see how many votes they need to manufacture to win certain districts.
Dems flubbed that in 2016, but learned how to do it better in 2018.
Do it on a Saturday. Allow seniors to vote on Friday for 8 hours to clear any logjam that might develop. No more early voting without I.D. + fingerprinting. Fingerprinting for all.