In American political jargon, an October surprise is a news event deliberately created or timed to influence the outcome of an election, particularly one for the U.S. presidency.
The President of the United States of America is the elected head of state and head of government of the United States.
Jargon is a type of language that is used in a particular context and may not be well understood outside of it.
Politics is the process of making decisions applying to all members of each group.
Julian Assange - Hillary's October Surprise by LibertyPen
The reference to the month of October is because the date for national elections is in early November.
Election Day in the United States is the day set by law for the general elections of public officials.
October Surprise: WikiLeaks to Drop Clinton Foundation ... by TheDailyTrump
Therefore, events that take place in late October have greater potential to influence the decisions of prospective voters.
Since the 1972 presidential election, the term "October surprise" has been used preemptively during the campaign season by partisans of one side to discredit late-campaign news by the other side.
The United States presidential election of 1972 was the 47th quadrennial presidential election, held on Tuesday, November 7, 1972.