So: On the eve of war, the Kennedys go to the Riviera, where they hang out with a lot of stars, including Marlene Dietrich. He was famous for liaisons with "showgirls and ingénues" and a long affair with Gloria "Sunset Boulevard" Swanson, who described him as "'like a roped horse, rough, arduous, racing to be free,' yet within minutes, his lovemaking was over with 'a hasty climax.'" Anyhoo, Dietrich, who was on the Riv with her husband Rudi - "a blond, good-looking young man-about-town who could have passed for her brother" - and her current lover, said of Joe, "he was old then already, but sweet," so obviously they had to have an affair.
In case you're wondering how the man-about-town took it, well:
Marlene ... considered it the norm to have her current lover, her husband, and her husband's lover out and about as a foursome. Some of her devotees, such as Maurice Chevalier, took this in stride, sending white lilacs to Marlene and cornflowers to Rudi (Rudi's preference for his lapel). Others, like the British-born charmer Brian Aherne, her co-star in The Song of Songs, objected to the arrangement. "Sweetheart-you must be joking!" responded a baffled Dietrich. "All this soul-searching about poor Rudi. He is my husband! What has that to do with it? You can't be that bourgeois."
The two publicly liaised throughout the summer, argued politics (she couldn't convince him of the dangers of Nazism) and at one point she slipped her hand down 21-year-old Jack Kennedy's pants at a dance, like ya do.
She clearly thrived on pleasing her partners and didn't believe in condoms, finding men "so grateful when you tell them they don't have to wear it." Once she discovered diaphragms, she called them "the greatest invention since Pan-Cake makeup." Until then, she had sworn by her secret weapon against pregnancy: douching with ice-cold water and wine vinegar, which she carried with her by the case everywhere she went.
Next summer on the Riviera, Joe had a rival for Marlene's affections in the person of the dashing lesbian Jo Carstairs, known for her speedboat racing prowess and the doll, Lord Tod Wadley, she carried with her everywhere. (That's not in the piece; I just happen to be very fascinated by Lord Tod.) However, they picked up again, he convinced her to take a comeback role in Destry Rides Again (on the set of which she had a well-known affair with Jimmy Stewart), and the two kept up a lifelong friendship.
When she was 60 and JFK was in office, he invited her to the White House and in a move that obviously had nothing to do with Daddy issues, he made a "pass." As Gore Vidal (obviously) tells it,
her initial protest of "You know, Mr. President, I am not very young" soon gave way to "Don't muss my hair. I'm performing." After an "ecstatic three to six minutes," Jack fell asleep.
She then makes her son-in-law smell her panties to prove it. Vanity Fair: unromanticizing legends since 1913.
It Happened at the Hôtel du Cap [Vanity Fair]