Reported in A Plan to Mine the Minnesota Wilderness Hit a Dead End. Then Trump Became President. (The New York Times, 6/25/2019)
The Merriam-Webster entry does not include a hyphen between the words whereas the New York Times article does.
According to Merriam-Webster, the first known use of the compound noun "game changer" occurred in 1993.
Other coinages from the same year include:
- access provider
- body camera
- booty call
- dwarf planet
- jukebox musical