What there is evidence for is that the voting machines are not secured as well as an ATM or a slot machine - that has been known since 2000 and nothing has been done to improve the security or the ability to audit the elections.
There is indisputable evidence that in GOP controlled states a Democratic vote counts for less than a Republican vote because of gerrymandering. That illegal voter purges is systematically being used to remove eligible voters from the rolls (North Carolina, Ohio were caught but a number of other states used the same software) without providing chances for the voters to prove they are eligible. That in many places provisional ballots for voters who are challenged are less often counted and that vote by mail ballots are often disqualified without giving the voters a chance to dispute it. That polling locations in mostly Democratic areas are being reduced and that voting machines are less well maintained in some of those areas.
While I was encouraged that the Clinton campaign here worked hard at voter registration, for the future I think Democrats need to concentrate on making sure all voters exercise their right to vote and that every vote is counted. The Republicans have spent decades trying to make voting more difficult with little push back from Democrats. We need to turn that around!