Can you judge a candidate's character by the way he treats his wife and family?

Of course you can. What a presidential candidate does for his wife, signifies how he will look out for the people of America. If he treats his wife with respect and values her highly then its likely he will do the same for those around him. Whatever you hold dear to your heart that is where you will be and spend time. So if he cares that much about his wife, he will probably care that much about others. Being in marriage requires commitment and an undying love. You can't be selfish and survive in marriage. So the same goes for the presidency. You can't be selfish because you are there to serve the people...