An election surprise (also a pre-election surprise, or, in the U.S., October surprise, where elections are held on the first Tuesday after the first Monday of November) is an event which occurs preceding an election which has enough shock value that it may be able to sway voters in close elections. When planned, an election surprise may be an act of propaganda. Election surprises typically fall into categories such as terrorism, political scandals, etc.
There may be disagreement as to what constitutes an election surprise for several reasons:
Rumours of potential election surprises may also abound preceding an election.
The term "election surprise" may also be used to denote an election with a surprising outcome.
United States
References
Election surprise Wikipedia(Text) CC BY-SA