Were there presidents and first ladies who were on the verge of divorce when he was elected President of the United States?
I have never known any presidential candidate couples intimately enough to speculate on the state of their marital relationship. Many of the male candidates had "rumors" of extra-marital women, FDR and Eisenhower come to mind. Eisenhower's long-time driver, Kay Sommersby, was long "believed" to be his mistress among the upper echelons of the military.
I can't imagine how anyone in the general public would know the marital condition of a candidate couple, unless they had once filed divorce papers or for a legal separation.