I don't know if he steamrolled her opinion. Maybe his decision to keep campaigning is just a form of denial. It might be easier to focus on running for the White House than to sit at home and face your wife's terminal illness. Regardless, I wish Mrs. Edwards the best.
She was so in denial that she made them take him off morphine, because she didn't want him to get addicted so he spent the last week of his life in agonizing, unchecked pain until the last 2 days when I threw a crazy in the hall with the Dr. who was almost in tears himself because he had no say in the matter, I finally talked her into some Demerol.
Denial is a strong emotion, it can protect us from unbearable pain but it can get in the way too.