voter fraud happens, not usually enough to swing an election

 NRO Morning Jolt Nov 2020 https://www.nationalreview.com/the-morning-jolt/a-careful-voter-fraud-review

vote-fraud ruling shifts pennsylvania senate

 1994, judge overturns philadelphia election, gives seat to R

https://www.nytimes.com/1994/02/19/us/vote-fraud-ruling-shifts-pennsylvania-senate.html?searchResultPosition=1

california motor voter registration leads to bad voter rolls

 https://www.latimes.com/california/story/2019-08-09/duplicate-voter-records-audit-california-motor-voter-system

Heritage Foundation database of voter fraud cases

 https://www.heritage.org/voterfraud

Arrest in Texas fraudulent absentee ballot request

 https://texasscorecard.com/local/north-texas-mayoral-candidate-arrested-for-dozens-of-mail-ballot-voter-fraud-felonies/

history of election fraud in Philadelphia

 from the Philadelphia Inquirer  9/30/2020

The city’s most infamous election fraud case came during a 1993 election for a state Senate seat. Bogus absentee ballots were filled out to benefit the Democrat, William Stinson, who received 79% of the vote. A federal judge threw out the ballots, ruling that election officials had illegally distributed many of them to campaign and Democratic Party workers. Stinson was removed from office...

Philadelphia had an actual case of election fraud in 2017, during a special election for a state House seat. Pennsylvania Attorney General Josh Shapiro charged polling place workers with intimidating voters, casting bogus ballots, and falsely certifying results. The Democratic nominee won that race with 73.5% of the vote, so the illegal acts were unlikely to have had much impact on the results.

Another case of election fraud went public this year when a South Philadelphia judge of elections pleaded guilty to federal charges for taking bribes to inflate votes for Democratic candidates.