The USA has a long history of vote fraud. Compared to other Western countries, it is quite staggering.
Ohio 2004 was one of the dirtiest contests. Ken Blackwell told Ohio's counties that they could destroy election records in defiance of a court order that required the counties to keep those records. We'll never know the truth about what happened in that election.
And then there were those exit polls that were extremely accurate in the 30 or 40 non-battleground states but not in the battleground states where Bush got more (official) votes than the exit polls predicted. Strange and highly unlikely.
Though the GOP seems to be the most corrupt lately, the Democrats have done their fair share to undermine the integrity of elections. Who could forget LBJ's popularity with dead voters?