Before revision: An election surprise (also a pre-election surprise, or, in the U.S., October surprise, where elections are held on the first Tuesday 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.
After revision: after the first MondayAn election surprise (also a pre-election surprise, or, in the U.S., October surprise, where elections are held on the first Tuesday 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.