Since McKechnie was in the same season as Rose, it was three times in two seasons.
I will say that in 1976, I felt McKechnie belonged in leading. I understand why people, including it seems Verdon and Rivera, felt otherwise. My feeling is that the dramatic climax of the show is Cassie's, and that made her the pivotal character in a show that otherwise really didn't have one. Perhaps with replacements in the original and in revivals, Cassie has not seemed like anyone in that role could be considered leading, but with McKechnie at least, I felt she belonged there.
That same season, I think a strong argument can be made that the only man who belonged in leading actor in a musical was Ian Richardson.