The "perfect" electoral system would ensure that everyone who has the right to vote can indeed do so, do so only once, and that no one who is not entitled to vote does not. Simple, eh? Not so much! Let me itemize some of the complexities that lead to data ambiguity.
- Registration to vote has to be completed ahead of time (in many places).
- The placement of a candidate on the ballot has to be done ahead of time, but write-in candidates are permissable under some circumstances..
- Voters may vote ahead of time.
- Voters vote in the precinct to which they are assigned (at least in some places)
- Voters may mail in their votes (absentee ballots)
- What if a person votes ahead of time, and then becomes "ineligible" prior to voting day. Possible causes include death, conviction of a felony, certifiably insane.
- What if a person moves after registration, but before they vote?
- What if a candidate becomes unfit after the ballots are printed and before early voting? (death, conviction of a felony, determination of status - eg not a natural born citizen
- What if a candidate becomes unfit after early votes for that candidate have been cast?
On a more serious note, voting systems deliver inherently ambiguous results. Fortunately that ambiguity is tiny, but in ever closer elections, it gives those of us who think about systems somethings that are very hard to think about. That is, "How do we ensure the integrity of the total process?" and "How good is good enough?"
Actually that thinking should always apply. While we focus on the happy paths (the majority case), we should always be thinking about what the tolerance for error should be. It is, of course politcal suicide to say that there is error in the voting system, but rest assured - even without malice, there is plenty of opportunity for errors to creep in.