WASHINGTON >> To the long list of rich-guy foibles that turned into defining campaign moments — John Edwards’ $400 haircut, John Kerry’s kite-surfing, John McCain’s inability to remember how many homes he owns — let us now add Newt Gingrich’s $500,000 revolving line of credit at the luxury jeweler Tiffany & Co.

The way Gingrich sees it, as he said on “Face the Nation” on Sunday, he’s “a guy running for president who pays all of his bills,” who lives within his budget and is in fact “very frugal.”

The way some voters out in the rest of America might see it, he’s a guy who paid more for jewelry than some people pay for their houses.

It has been a week since Politico broke the news that while working for the House Agriculture Committee, Gingrich’s wife, Callista, filed forms for 2005 and 2006 disclosing her husband’s “revolving charge” of $250,001 to $500,000 with Tiffany. Gingrich, insisting his jewelry buying habits are his own business, has declined to say what he bought.

But the glittering strand of diamonds that Gingrich wore last month to the Washington premiere of the couple’s latest documentary movie looks strikingly like one that Tiffany advertises for $45,000. And Time magazine’s website Tuesday posted a slide show of Gingrich wearing various baubles that seemed from the Tiffany catalog, including what looks like a $22,000 pair of diamond and gold starburst earrings “inspired by electrons orbiting in the nucleus of an atom.”

Tiffany’s or knockoffs? The Gingrich campaign won’t say. But at this point, it no longer matters, according to political strategists of both parties. What matters, they say, is that the Tiffany story is sticking to Gingrich, helping to define — or perhaps redefine — him in the critical early days of his bid for the Republican presidential nomination.

As House speaker, Gingrich preached the virtues of fiscal conservatism; now he is struggling to explain how spending large sums on jewelry fits in with that philosophy. And while a spokesman for Tiffany confirmed Tuesday that Gingrich had paid the debt in full, with no interest, parrying questions about a six-figure jewelry bill is hardly what his campaign needs at a time when many Americans are out of work or have lost their homes.

The episode also reinforced what campaign strategist like to call “negatives” — in Gingrich’s case, questions about his personal life, which includes two divorces and a six-year secret affair with Gingrich, then Callista Bisek, when she was a House aide and he was speaker.

The Gingrich campaign had hoped that, after 11 years of marriage, he could present himself as a stable family man.

Now Gingrich is the butt of yet another round of late-night television infidelity jokes.

“Five hundred thousand at Tiffany’s?” comedian Stephen Colbert asked. “There’s a simple explanation. The guy clearly buys his engagement rings in bulk.”

In Iowa, where Gingrich drew big crowds last week, the Iowa Republican, a political website, ran a scathing commentary titled “How a Fiscal Conservative Spends $500K at Tiffany’s.” The site’s editor, Craig Robinson, a former political director for the state Republican Party, said the essay was submitted by a political activist who was “completely turned off” by the expenditures.

“It’s bizarre; I don’t think he’s ever going to live it down,” Robinson said. “There aren’t many $500,000 homes in Iowa, so we can’t even fathom $500,000 in credit card debt, let alone to a high-end jewelry store.”

On CBS News’ “Face the Nation,” Gingrich called the credit line a “standard, no-interest account.”

The Tiffany spokesman, Carson Glover, said the company offers customers a “revolving credit card agreement” with state-specific rates; those who hold such cards are eligible for up to 12 months of interest-free borrowing if they spend more than $1,000 on an engagement ring or $5,000 on other merchandise.

Gingrich, of course, is hardly the first politician to become a sudden symbol of spending excess. In the 2008 campaign, Sarah Palin, the Republican vice-presidential nominee, presented herself to voters as an ordinary “hockey mom,” only to face revelations that the Republican Party had spent $150,000 on a designer wardrobe. Edwards styled himself “the son of a mill worker,” an image contradicted by his pricey haircut.

Gingrich’s situation “is sort of a twofer, which is why it is particularly damaging,” said Chris Lehane, a Democratic strategist. It raises questions about his commitment to fiscal restraint, Lehane said, and also “plays into a prevailing story line about lack of discipline and being reckless, which has been a consistent part of his political and public life.”

Gingrich, who has grown wealthy in recent years by publishing books, making movies and delivering speeches, says it is not recklessness at all; on “Face the Nation,” he said that he owes no money except for his mortgage payments on one rental property in Wisconsin, his wife’s home state.

“If the U.S. government was as debt-free as I am, everybody in America would be celebrating,” he said. “I think I have proven I can manage money.”

But out in Iowa, Robinson says buying jewelry on credit somehow feels different from buying a refrigerator or a new washing machine.

Rich Galen, a former Gingrich aide, agrees.

“It’s not something that normal people do,” Galen said. “I understand he’s made a lot of money and he’s done very well, and God bless him for it, but that’s sort of a departure from the Newt Gingrich that I knew.”