Is it common practice for a sitting U.S. President to cheat on his spouse?

Kennedy. Roosevelt http://www.romanceopedia.com/H-11.html
That I know of…...

Here’s a list of Presidents who have been engaged in extra-curricular sex.

THOMAS JEFFERSON
GROVER CLEVELAND
WOODROW WILSON
WARREN HARDING
FRANKLIN ROOSEVELT
DWIGHT EISENHOWER
JOHN F. KENNEDY
BILL CLINTON

I mean I’m sure there have been some we don’t know about to add to those we do… But I’d like to think its not “common-place.”

If you venture into conspiracy-ville, you might come to see that it’s ubiquitous and probably has more to do with a cult(ure) of power than the typical elements of “love affairs.” Lots of homosexual sex among men, ritualized sex, and people programmer at an early age with multiple personalities including ones that are sexually submissive.

There’s an old GHW Bush clip where he says (referencing a meeting with Reagan) “we had some sex.” Most people wrote that off as a Freudian slip, but perhaps it was said at face value.

Where is George Bush the I on your list @wundayatta? It was well known that he had a mistress.

“In his diary, he wrote: “Spent the last two days out of that Sheraton Waikiki madhouse and in the 4999 Kahala apartment — just lovely . . . Checked out the bathhouse again . . . Totally relaxing. Someday I will write a book on massages I have had . . .

“I must confess the Tokyo treatment is the best. Walking the back . . . combination of knees and oil . . . does wonders for the sacroiliac, and a little something for the morale too . . . Flew back to Peking on Iran Airlines. Jennifer and I alone in first class.” ”

Source

they’re just men after all, not gods.