October Surprise is the allegation that representatives of the 1980 Ronald Reagan presidential campaign arranged the Iran-Contra deal well in advance of the 1980 election where Ronald Reagan defeated Jimmy Carter. October Surprise is also the title of a book on the subject by Gary Sick. This usage of the term describes a situation where a Presidential incumbent uses his office to do something very popular at the last minute before election day, to increase his chances of getting reelected. Thus the alleged conspiracy was precisely to prevent an "October Surprise" that would have aided Carter, the incumbent, effected by postponing the release of the hostages held by Iran until after the election. The allegations are not vague.
http://www.worldhistory.com/wiki/O/October-Surprise.htm

Carter was at the time dealing with the Iran hostage crisis and the hostile regime of the Ayatollah Khomeini. Those who aver that a deal was made allege that certain Republicans with CIA connections, including George H. W. Bush, arranged to have the hostages held through October, until Reagan could defeat Carter in early November, and then be released. The hostages were in fact released on the very day of Reagan's inauguration, twenty minutes after his inaugral address. If the timing was a double-cross that was meant to tip off the American public to the game, it failed to elicit much commentary.

A 1981 Congressional probe into the Reagan campaign's theft of White House briefing books on the eve of a presidential debate disclosed that Reagan campaign manager William Casey (later CIA chief), was receiving highly classified reports on closely held Carter administration intelligence on the Carter campaign and the Democratic president's efforts to liberate the hostages.

If this is how events happened, some believe that dealing with a hostile foreign government to achieve the defeat of a domestic administration would have been an act of treason.

According to Sick's analysis, Oliver North was more or less a fall guy, taking the responsibility in order to conceal the treason of Reagan and Bush.