The OED traces the domino theory to a speech by Dwight Eisenhower that
was quoted in the NY Times of 8 April 1954. William Safire's NEW POLITICAL
DICTIONARY discusses it in detail and adds "The phrase has currency."
In the Chicago Tribune of 21 June 1917, pg. 13, col. 2, there is a
drawing of dominoes. A hand represents "The People." The dominoes about to
fall include a czar, a king, and a kaiser.