Computer Programmer Clint Curtis testified to a congressional committee in 2004, that he was paid to write a program for a prominent Florida Republican which could flip votes and be undetectable. This shows Republicans history of efforts to rig / flip elections so it would be undetectable.

Full testimony of veteran computer programmer Clint Curtis, at a U.S. Congressional Hearing in 2004 about being contacted by a Florida Republican to create election rigging software

RedShift: How The GOP Rigged Our Elections

Voter Suppression has been a Republican tactic for the last 50 years. Author Thom Hartman reveals one particular effect of their voter suppression, Redshift