When the sordid story of South Carolina Gov. Mark Sanford’s affair with an Argentinian woman made headlines last June, his wife came across as a new role model for political wives. Instead of standing by her man while he confessed his infidelity in a rambling, embarrassing appearance on national TV, Jenny Sanford let him deal with the press in his own inept way. She later issued a statement saying she had asked her husband to leave.

In Staying True (Ballantine. $25), however, instead of admiring Jenny Sanford, I found her too often playing the martyr to her self-absorbed, cheap, womanizing husband and father of her four sons, ages 17, 16, 13 and 11. Why in the world would an intelligent woman with her background stick it out for over 20 years and continue to defend him?

The author was a successful investment banker on Wall Street when she met Mark Sanford, then finishing his MBA at the University of Virginia, and there were plenty of warning signs he would make a lousy husband.

They had barely started dating when he invited her to spend New Year’s weekend at his family’s farm in South Carolina. But instead of meeting her at the airport, he leaves his stick-shift car, which she doesn’t know how to drive, for her to manage on her own through foggy roads of unfamiliar country.

When they decide to get married, he insists on reworking the wedding vows, leaving out the promise to be faithful. Every woman I know would immediately spot a red flag at that point, and Jenny Sanford admits that “in retrospect, I suppose I might have seen this as a sign that Mark wasn’t fully committed to me.” But she rationalizes that she saw it as “a classic case of pre-wedding cold feet” and writes that she had “unshakable faith” in him.

Later, he turns out to be a true cheapskate, once returning a diamond necklace she loved that he had given her for her birthday. “He could see I was disappointed,” Jenny Sanford writes, though she again rationalizes his inexcusable deed. “In truth, once I knew he thought he had overspent, I also knew it would pain him to see me wear the necklace had I insisted on keeping it. I wouldn’t have felt comfortable wearing it in his presence, so what was the point.”

One of the most amazing stories in Staying True is when Mark Sanford begs his wife’s permission to continue seeing his mistress in Argentina after the affair had gone public.

“Mark still saw me as his sounding board,” writes Jenny Sanford, who had often worked as his campaign advisor. “. . . He wondered aloud to me if he shouldn’t just follow his heart. What if he could find true happiness only in Argentina? Would he always live his life in regret, in wonder, because he didn’t take this chance? Clearly, these were thoughts I wished he’d kept to himself.”

And although her husband never told her, she would learn secondhand that he had also had other “dalliances” over the years.

It's hard, when starting to read this book, not to feel sorry for Jenny Sanford. Later on, it’s hard to understand why she put up with so much or to feel much sympathy for an educated, intelligent woman who allowed herself to be treated so badly for so long.