WATERLOO, Iowa -- Perhaps the most poignant moments on the campaign trail with Newt Gingrich have involved his wife, Callista Gingrich.

There she is at Southbridge Mall in Mason City, gently telling him not to eat a scone in front of the television cameras.

MASON CITY, IA - DECEMBER 28: Republican presidential candidate former Speaker of the House Newt Gingrich (R) and his wife Callista Gingrich (C) greet workers at a nail salon at Southbridge Mall in Mason City, Iowa. (Photo by Scott Olson/Getty Images (Scott Olson/GETTY IMAGES)

And there she is, at L.J.’s Neighborhood Bar and Grill in Waterloo, watching as a voter asks him to describe his greatest weakness.

The former House speaker turned to his wife as if to prompt her to answer the question. Go ahead, she seemed to say as she threw her hands up and smiled.

When he answered, he spoke not of his personal life but of his regret for not pushing back harder against the TV attacks that have indundated the Iowa airwaves for much of the month of December.

But his private life, and the marital history Bonnie Goldstein wrote about here yesterday, is a subtext that never really goes away. Callista Gingrich is, after all, her husband’s former mistress, the third wife now but the woman with whom he conducted a six-year affair while he was speaker of the House.

Whether intentionally or not, the image she presents is all wife and no mistress. Formal and reserved in her red blazers, ruby lipstick and stunningly coiffed platinum hair, Gingrich does nothing if not project the portrait of political spouse. One wonders if she does so precisely because she is debuting in the role after all those years as the other woman.

So, too, does one wonder if that image helps hide the sheer terror most of us would feel if we were asked to live through that transformation.

Callista Gingrich clearly has grown more comfortable with her new role, appearing more often by her husband’s side as he addresses crowds. She introduced him at a pizza joint in Decorah that sits below the apartment she lived in as a senior at nearby Luther College. She speaks more readily to voters and journalists. She talks about her very rich life as a French horn player with the Fairfax City Orchestra and a choir member at the Basilica of the National Shrine of the Immaculate Conception. And she has genuinely embraced a few campaign duties that please her: producing a video promoting musical education and helping launch a lighthearted web page called “Pets With Newt” that showcases her husband’s passion for animals.

Where the campaign goes from here for the Gingriches is, of course, unclear. The outlook is not particularly bright. But if there’s one thing Callista Gingrich has proven on this grueling journey, it’s that she will stand by her husband, stop after stop, day after day. He may need that more than ever in the weeks to come.

Amy Gardner is a political reporter for the Washington Post.