We know ((they)) have to tell you in advance.
Kenneth Arrow, NobelPrize winner in economics, defined some basic characteristics that a democratic system should seek to provide, and then showed why they were mutually exclusive. These characteristics were:
Universality The voting method should provide a complete ranking of all alternatives from any set of individual preference ballots.
Monotonicity If one set of preference ballots would lead to an an overall ranking of alternative X above alternative Y and if some preference ballots are changed in such a way that the only alternative that has a higher ranking on any preference ballots is X, then the method should still rank X above Y.
Independence of irrelevant alternatives If one set of preference ballots would lead to an an overall ranking of alternative X above alternative Y and if some preference ballots are changed without changing the relative rank of X and Y, then the method should still rank X above Y.
Citizen Sovereignty Every possible ranking of alternatives can be achieved from some set of individual preference ballots.
Non-dictatorship There should not be one specific voter whose preference ballot is always adopted.
An example: You have a group of 100 voters. There are two candidates, A and B. The votes split like this:
A: 55 votes.
B: 45 votes.
If we introduce candidate C into the mix, we should now have two possibilities: A should win, or C should win. B should not be a contender. However, C is to A as Ralph Nader was to Al Gore, and the new voting pattern looks like this:
A: 44 votes.
B: 45 votes.
C: 11 votes.
A simple "first-past-the-post" system, where the winner is the person with the most votes, has violated the criterion of independence.