Seriously: the system allows voter fraud to occur without check. The States control the Presidential Elections in each State. The Democrat States have consistently refused to ask voters for proof of their ID, so anyone can turn up at a booth, say “I am Joe Smith” and vote. There are no systems for catching people who vote under several names at multiple polling booths.
The evidence produced by the right was achieved by a sting operation: Project Veritas infiltrating the Democratic Campaign and recording their organisers boasting about organising voter fraud on a grand scale. http://projectveritasaction.com/video/veritas-voter-fraud-compilation-voterfraudisreal
The Democrat response was to say the videos are faked, but they fired Scott Foval after it was released. Since then they just say the report has been debunked, without ever actually doing so.