What is the history behind the “Ex-Cub Factor.” What is it, exactly how did it get started, and how is it connected to the World Series?

The Ex-Cub Factor was a phrase coined by Ron Berler in a 1981 Boston Herald article. In it, he stated that since the 1981 New York Yankees had five ex-Cubs on their team, they were doomed to lose in the World Series. He was right – they fell to the Los Angeles Dodgers in six games. Berler went on to say that players who had played for the Cubs carried with them a part of “Cubness,” or failure, that stuck with them their entire careers, and no team with too many ex-Cubs could ever be successful.
As it stands, since 1945, the last year the Cubs won the pennant, only one team with three or more ex-Cubs has gone on to win the World Series — the 1960 Pittsburgh Pirates.