...never had an affair

https://www.metv.com/stories/mary-tyler-moore-called-it-a-terrible-waste-that-she-and-dick-van-dyke-never-had-an-affair

They saved the chemistry for the screen.

Mary admitted in one of her books that she rejected Dick Cavett mainly because he's short in stature.

Apparently Van Dyke was more to her liking, being tall of course.