DNA Is Said to Solve a Mystery of Warren Harding’s Love Life

[Houmes]

Grover Cleveland was another President with a paternity scandal, I believe. It has lived on through a political cartoon published at the time.

A Secret Life: The Lies and Scandals of President Grover Cleveland
by Charles Lachman

If even half of this book is correct, it's a fairly good example of jaw-dropping, eye-opening moral turpitude.