There's compelling evidence that electronic vote tallies were tampered with during the 2020 primaries.
Bernie Would Have Lost
https://web.archive.org/web/20201105081005/http://berniewouldhavelost.com/
How the rigging of the 2020 Democratic Primary demonstrates why Bernie Sanders could never have won the general election
One of the most striking lines of evidence is the exit poll discrepancies. There were discrepancies in regions with electronic voting, but not in hand-counted regions, and the discrepancies were almost always biased against Sanders.