That question would be meaningful if that was the entire range of options, and it's not. A person can marry another person who, over time becomes a poorer and poorer companion. Maybe they started out fine, and became more loathsome over time. This change need not happen overnight.
Also some people just marry a poor choice for a spouse from the beginning, and come to realize it years later, after a lot of angst and aching.
Also, someone can be a good spouse and things can deteriorate quickly - they can become smitten with a coworker, for example, and have no interest in cultivating their relationship with their spouse.
Someone can be a good spouse and because of increasing work demands neglect their spouse. Often they don't intend to do it, it just happens over time. They make the series of decisions at the expense of their marriage and the alienated spouse finally calls them on it, and finds someone better.
Second, how do you know Newt's wives were loathsome? Seems rather a rush to judgment on your part against two women you don't know at all.
My comments were not regarding Newt at all, but against the general principle that leaving a spouse inexorably makes for a lousy person. I don't think leaving a spouse, or cheating on a spouse (in a certain set of circumstances) necessarily makes a person bad. Indeed, there are some conditions where it can be a good thing.
It is a sin and a serious one, violating a Commandment. How can that be a good thing?