Political parties, candidates and the media conduct polls to gauge voter support for the different candidates or parties. Polls are also used to focus campaigns and to develop and improve messages for voters. When the results of a poll are announced publicly, the methodology used should generally be made public so that users may assess the accuracy of the poll. In Canada, this information includes the names of whoever conducted and commissioned the poll, the timing of the poll, the sample population, the number of people contacted, the margin of error for the results presented, the wording of questions asked, and instructions on how to obtain detailed information on methodology.
The timing of the release of poll results may be an integrity issue. The results may influence undecided voters and create momentum in favour of a candidate. Thinking that the election has already been decided, people might choose not to vote.
To avert such problems, some systems prohibit the release of poll results at strategic times, usually immediately before election day. These rules may vary; in Mexico, for instance, it is an offence to release a poll predicting the winner less than eight days before voting ends. In Canada the law prohibits the publication of opinion poll results during the last three days of the electoral campaign, while in Denmark there is no restriction on the publication of polls.
