"While he cheated on her, she was the dutiful wife who stayed with him "for better or worse."
While he cheated on her she stood by his side and disparaged every one of his girlfriends/conquests/victims. That is precisely why the marriages of other candidates is not an issue.
Long ago a major league scoundrel [Vladimir Lenin] described another scoundrel [Leon Trotsky] as a "political prostitute". Now, the expression is apt. Political prostitutes cannot be "dutiful wives" even when they are, for no one would believe them anyway.