Harding and Phillips were both married at the time, which would have made the letters much better news fodder back in the late teens that they are now. Harding ran successfully for President in 1920. He wanted a "return to normalcy" after WWI and what had been seen as the much too "liberal" Wilson administration. Such a torrid love affair would not have fit with the staid image he cultivated of himself, but seem to be the only thing worth noting from his conservative life.
There were other affairs too, including one with Nan Britton, whose daughter she claimed was his. The GOP did its best to keep these juicy stories under wraps in the 1920 election. Nan was certainly the most fetching of the two, and 31 years younger than the Republican presidential nominee.
His administration was probably best known for the Teapot Dome Scandal, which ushered in oil influence peddling in the 1920s. However, his tenure was cut short by a stroke of apoplexy on August 2, 1923, just two-and-a-half years into his first term. He was succeeded by the equally staid Calvin Coolidge, presiding over probably the least memorable period in U.S. Presidents, 1920-1932, with the election of Herbert Hoover in 1928. Big Business reigned supreme, with virtually nothing to regulate their interests, resulting in the worst stock market crash in history.
James D. Robenalt has certainly added a lot of intrigue to the romance. He claims that Phillips and her daughter became German spies during WWI, and may have conspired with Harding to keep him out of the Presidential race in 1916, as it was in Germany's interest to keep the US out of the war. Robenalt would like us to think that "counterfactual arguments abound" in the over 800 pages of correspondence between the two, but it strikes me as just a hook to read his book.