A. The term originated at The Blackstone Hotel in Chicago where, in June 1920, Republican party leaders declared Ohio Senator Warren Harding the party's "surprise nominee." (At the time, two other party candidates were in a dead heat.)
According to my source, an April 30, 2008 Reuters News blog by Andrew Stern titled, "The origins of "smoke filled room" (Tales from the Trail - Tracking the 2008 U.S. Campaign), Mr. Stern also offers the following details:
"Legend has it that a cloud of cigar smoke poured from the room as they came out to make the announcement to assembled journalists, who coined the phrase that entered the American political lexicon. It refers to a behind-the-scenes move by party bosses to pick candidates.
Some historians credit Harding’s friend Harry Daugherty with creating the phrase ahead of the convention. Harding was subsequently elected the 29th U.S. president." | 
