Ok, Ann Romney is not unattractive but she is diseased: a characteristic that likely leaves her acutely uninterested in sex. Her affinity with horses suggests that coregasms are at least theoretically possible so she doesn't need to have sex with Mitt:
Mitt is a powerful capitalist with needs:
...even Ann admits how stiff he is:
Penile implants are nearly ubiquitous for older men like Mitt and the procedure is covered by Massachusetts' RomneyCare.
If Romney isn't having an affair he is not fit to be President: it's just that simple.