<P> The principle of such election rules in a club is that it is self - perpetuating to preserve the current ethos (and exclusivity) of the club, by ensuring that candidates are congenial to (almost) all the existing members; i.e., new members are elected by unanimous or near - unanimous agreement of voting members . A difference of opinions could be divisive, so that an election must be taken secretly as well as correctly . </P> <P> The number of votes in support is often irrelevant, except to prove a quorum . Whilst in many such cases even a single black ball will be fatal to the candidate's election, rules in larger clubs ensure that a single member cannot exercise a veto to the detriment of the future of the club . For example, two black balls are required to exclude; a limited category or committee of members vote, rather than all members; or in the event of a blackball, the election may be repeated immediately to ensure that there is no mistake, or after a fixed period to allow further information or opinions to be discussed discreetly . A variant sometimes used is that all incoming candidates are voted on as a group; if the group as a whole is blackballed, then each member must be voted on individually . </P> <P> The practice also found popularity in areas outside of social clubs . In the Soviet Union, dissertation panels would typically cast their vote on a thesis defense using this system . </P> <P> Robert's Rules of Order notes that the use of black and white balls can be ordered by passing an incidental motion to that effect . The manual notes, "This custom, however, is apparently declining ." </P>

Where did the term black ball come from