Warren Harding was an average president. His reputation as the "worst president" has a lot to do with his averageness. Since no one feels really strong about him, historians can talk smack about him without seeming overly partisan, the way they wouldn't if they went after Reagan or FDR. He was corrupt but his corruption pales in comparison to lobbying practices that are legal today.
Such was the assessment that I saw of one (pre-Dubya) ranking of the Presidents. Ordinarily the unspoken requirements of the job is that one be above-average in morals, political skills, and overall intelligence. Harding was 'average, average, average'. Maybe a little above, but not by much. He would have been just the person to be a real-estate broker, a factory foreman, the chief officer of a savings-and-loan, a school headmaster, or a local chief of police.
The author excused a President who had an affair because of a frigid wife (FDR, Eisenhower) or had a long-time relationship with a slave woman that he treated as a wife after he became a widower (Jefferson, whose quasi-wife was a close relation to his deceased wife) -- but not someone who slept with anything that moved, as did Harding. The rumors about JFK were not yet well known.
Harding showed very poor judgment in his sexuality and in his unfounded trust in Ohio cronies who would be caught up in the Teapot Dome scandal. Truly-wise people don't make so many such mistakes. It is highly unlikely that anyone so unqualified as Harding could ever become President of the United States again.
