Real controversies and conspiracies, and well-documented crimes committed by a government whether in the present or the past.
Scottish referendum rigging:
Youtube.com
Same thing happened in Australian Independence vote & Devolution referendum vote. Dead people receiving ballet papers, people with dual nationalities getting voting papers, adjudicators filling in ballots or switching piles, media saying its "too close to call". Problems where due to these strategies enabled by zero requirement for signatures, names or address details for those voting.
Perhaps a similar problem will plague the Brexit vote: Moddb.com