There’s been a temptation on the part of the opposition for the last couple of decades to make as much hay as possible when it’s discovered the US president has a mistress, or had one. This hasn’t always been so. Presidents of the past venerated by those finger-pointers and accusers have frequently had their affairs during a time when such matters were left for gossip columnists and rumor mongers.
Lucy Page Mercer Rutherfurd was one of two women believed to have been FDR’s mistresses. Lucy has the distinction, though, of being the only certainty. Eleanor found her letters to FDR. https://en.wikipedia.org/wiki/Lucy_Mercer_Rutherfurd
Then there was Ike. Commander of Allied Forces in Europe during the invasion, and Republican president after Truman.
All those years Ike was in office I never knew anyone to criticize him about that particular issue. If they hated him at all [and the rabid right wingers certainly did] they didn’t bring his private sex life into the conversation.
Then of course there was LBJ and his shenanigans too numerous to bother mentioning except one.
As far as I know Ford, Carter, Reagan and both Bush presidencies were either adultery-free, or discrete enough to keep it out of the public eye. As was Obama. Goes to prove some presidents have the good sense to either keep their peckers zipped up safely inside their pants, or go the extra mile to keep it out of the headlines.
And there’s no point even discussing Bill Clinton….. that one’s the record Trump is trying to beat with Stormy Daniels.
Maybe it’s time, really time for a woman president so we can put all this sexual scandal to rest.
Old Jules
So Far From Heaven 
Don’t forget Nan Britton, mistress of Warren G. Harding, who was 31 years younger than WGH! DNA tests confirmed in 2015 that her daughter Elizabeth was Harding’s child.
That Harding was a scurrilous rounder by golly. Old Jules