There is a lot of media attention to Donald Trump's statement he wouldn't unconditionally accept the result of the election. Unfortunately, Mr. Trump didn't think to answer the question by referring to the example of Al Gore in 2000.
It should be clear by now that election fraud exists. There are a few criminal convictions and many more anecdotal accounts. Yet in any election involving 120 million votes there will be some degree of fraud, error, or mistakes.
A recent news report brought up the 1960 election when Kennedy beat Nixon. Andrea Mitchell, presumably a liberal (since she's on MSNBC) stated that the election was stolen from Nixon. This prompted me to again look at the 1960 election results. While it's widely admitted that the Illinois result was fraudulent and Nixon likely won, it's less clear the full election was stolen from Nixon.
Assuming that the Wikipedia election numbers are accurate, the Illinois result was very close, just .19%. Other results were closer (Hawaii at .06%, a mere 115 vote margin). However, Nixon could not have won the election with Illinois alone, Kennedy would still have 274 electoral votes, above the 270 required. Nixon needed at least one more state to throw the election into the House of Representatives, or he needed a large state to win. Texas is normally mentioned since there is a widespread belief that Lyndon Johnson had long manipulated Texas elections. Yet Nixon lost Texas by a full two percent. This is harder to ascribe to fraud. One could more easily ascribe Nixon winning California to fraud the other way (he won by .5%, a quarter of the Texas margin).