Republican presidential candidate Newt Gingrich has dodged questions about his half-million dollar Tiffany & Co. tab all week. Now, it has been revealed that the House committee Gingrich's wife Callista worked for was heavily lobbied by the posh jewelry store.

Politico revealed last week that in her 2005 and 2006 filings with the House Ethics Committee, Callista Gingrich disclosed that the former House Speaker had between $250,000 and $500,000 debt with Tiffany & Co. while she was working for the House Agriculture Committee.

"It's a standard no-interest account," to CBS' Bob Schieffer Sunday. "We paid no interest on it. There was no problem with it. It's a normal way of doing business."

Over those those same years, Tiffany's doubled the amount of money they spent on lobbying, according to the Center for Responsive Politics. The company spent $200,000 in 2006 alone.

Lobbying firm Cassidy & Associates, Inc. has reported that "[m]ining law and mine permitting -related issues" was the jewelry retailer's specific lobbying concern.

Tiffany's is well known for their silver jewelry.

Newt Gingrich's 2012 campaign website gives no indication that his wife was involved with mining.

"During her tenure, the Agriculture Committee held hearings on a wide range of issues including biotechnology, bioterrorism, conservation, forest management, nutrition, rural development, trade, and welfare reform," according to her bio.

The disclosure by Cassidy & Associates also lists former Gingrich legislative assistant Christy Evans as a lobbyist for the organization.

The Washington Post's Glenn Kessler notes that it's anything but "standard" for Tiffany's not to charge interest on loans.

"[W]e looked at the current installment credit application form posted by Tiffany on its Web site," Kessler wrote. "That form shows an annual interest rate of 21 percent for the state of Virginia, where Gingrich and his wife live."

"That would be a hefty interest charge in a year—about $50,000 on a $250,000 loan," he added.

"It doesn't sound plausible to me," Ben Woolsey, director of marketing and consumer research at CreditCards.com, told the Post. "Store credit cards almost never carry these kinds of terms, and it is highly unlikely for an exclusive retailer like Tiffany's."

[H/T: SpyTalk]