(CNN) Seated before a panel of House lawmakers, Housing and Urban Development Secretary Ben Carson sought to put to rest the controversy surrounding the purchase of a $31,000 dining room set for his office that has put his job on the line.

"I left it to my wife," Carson told a House panel Tuesday. "I dismissed myself from the issues." Decisions about "the color and style" of the furniture, were left to Candy Carson.

With her husband's assertion that it was her decision, not his, that led to the order of the pricey dining set that became the subject of late-night punchlines, Candy Carson became the latest in a steady stream of Cabinet secretaries' spouses to steal the spotlight, either for taking an outsized role in their husbands' official agency work or by being ensnared in ethical flaps that have involved spousal travel.

Lola Zinke, the wife of interior secretary Ryan Zinke, has been a presence at agency events and an official trip to California.

And Veterans Affairs Secretary David Shulkin's wife, Merle Bari, was named in the scathing inspector general report about a European business trip that her husband took last month that found "serious derelictions," and concluded that Shulkin's then-chief of staff altered an email to justify the department paying for Bari to join Shulkin on the trip.

All told, the roles and levels of involvement of some Cabinet spouses are as different as the secretaries themselves and the departments they lead, but each has found themselves in the media spotlight that follows every twist and turn of the Trump administration.

"It's not normal to have spouses playing such a prominent role in the operations of agencies," Chris Lu, who was White House cabinet secretary during President Obama's first term, told CNN. "Clearly, political spouses are always involved in some sense, but it would be highly unusual to see them in official meetings or making decisions that affect the agency."

The cabinet secretary serves as a liaison between the President and cabinet departments and secretaries.

Agency involvement

Candy Carson's role has drawn scrutiny not just for the hand she had in her husband's office redecoration, but also for the role she's played in her husband's official work. And Carson has made statements on social media that come from accounts that bear both his and his wife's name.

Although many in the media would like to depict me as a victim who was "thrown under the bus", Ben and I are enjoying our 43rd year of marriage and we fully support each other in all endeavors and will continue to do so pic.twitter.com/Lj2NUi8VHC — Ben & Candy Carson (@RealBenCarson) March 23, 2018

Earlier this year, amid scrutiny, Carson called on his department's inspector general to "review" the role that his family members have played at HUD, saying in an early February tweet that he had been "under attack."

Carson isn't the only Cabinet secretary's wife to play a visible role in a federal agency.

Susan Pompeo, the wife of CIA director Mike Pompeo, has taken on an unusually active role, spending time regularly at Langley and traveling with her husband since last January, more than a half dozen sources told CNN. Pompeo doesn't have her own office, but is the "honorary chair" of the CIA's Family Advisory board, according to CIA spokesman Ryan Trapani, attending and hosting events often "in support of the agency."

While Trapani said that Susan Pompeo does not receive pay or control agency funds, sources familiar with the matter told CNN's Jenna McLaughlin that her work has led some employees who regularly work with Pompeo to believe that they are her employees and that she had adopted a permanent residence at CIA headquarters.

"Mrs. Pompeo's work on behalf of CIA officers and their families has been broadly praised and welcomed, particularly by officers stationed in the field. She has graciously volunteered her time, much like former director's spouses, to drive initiatives that specifically make the lives of CIA officers and their families better for nothing more than the proud satisfaction of helping the Agency achieve its mission," Trapani said.

Lola Zinke's presence at Interior meetings, as well as the hand she had in organizing official events, has also drawn scrutiny.

Documents obtained by Western Values Project under the Freedom of Information Act and first reported by Politico , show that Lola Zinke weighed in on the specifics of some agency events, including inviting some attendees to an April 2017 town hall for the Young America's Foundation at the Reagan Ranch in Santa Barbara, California.

She'd previously faced criticism for accompanying her husband on the California trip, during which she posted on Twitter a photo of herself in California Gov. Jerry Brown's office and, according to Politico, she joined her husband on meetings with Interior staffers in the state.

Daniel Franklin, a political scientist at Georgia State University, said that the role of spouses in the Trump administration may be particularly pronounced because "Trump appointees are generally hostile to the agencies over which they've been appointed," so they may lack support from the agencies they run.

"A cabinet official's spouse becomes a confidant of necessity when there is no support in the agency," Franklin told CNN. "Of course civil servants argue that they work for the public and not the administration and Trump doesn't seem to understand that."

"But that being said, my understanding is that the Department of Interior has disavowed Lolita Zinke's antics. And that Ben Carson has thrown his wife, Candy, under the bus. That makes them more Martha Mitchell than Hillary Clinton," Franklin said, referencing the wife of former Attorney General John N. Mitchell. Martha Mitchell became notorious when her husband worked for President Richard Nixon for her outspoken public comments on all manner of subjects -- particularly those directed towards her husband's critics.

Spousal travel

A growing number of President Trump's Cabinet secretaries have found themselves making headlines over how they travel, and in many cases, their wives play a role.

In the case of Louise Linton, it was a leading one.

The wife of Treasury Secretary Steven Mnuchin made headlines last year when she posted an Instagram photo of herself deplaning a government plane decked in designer clothes and accessories -- the post included hashtags identifying the brands -- and later directed a screed in the comments at a stranger who left an outraged comment.

The photo prompted speculation that Mnuchin had timed the trip so that he and his wife could have a prime view of that day's solar eclipse, and the ensuing controversy kicked off an investigation into Mnuchin's travel practices. Treasury's Inspector General found no evidence of wrongdoing.

Linton also made headlines when she and Mnuchin posed with sheets of new $1 bills bearing Mnuchin's signature last year.

At the Department of Veterans Affairs, Merle Bari, the wife of secretary David Shulkin, was at the center of an inspector general report that seemed to tarnish her husband's standing and was used by some political appointees within the agency looking to force his ouster.

The report released in February found that Shulkin's then chief of staff altered an email in order to justify taxpayers paying for Bari's travel on a trip to Denmark and England. VA paid more than $4,000 for her airfare, and Shulkin has reimbursed the treasury for it.

The report also found that Shulkin improperly accepted tickets to a Wimbledon tennis match and directed an aide to act as what the report described as a "personal travel concierge" to him and his wife.

Emails released as part of the inspector general's report showed emails between Bari and a VA aide in which Bari asked about tourist activities including "Roman baths in [Bath]" and "high tea." The aide, in an email included in the report, complained about Bari's requests, saying to a coworker :"I would have been finished with this a week ago."

Lola Zinke's travel has also drawn scrutiny, as CNN and Politico have reported, including her presence on a 2017 trip to Alaska on which staffers had to scramble to allow Lola Zinke to stay longer.

Documents, obtained by Western Values Project under the Freedom of Information Act, show that after an advance staffer learned that Lola Zinke would be departing at a different date than previously scheduled, the staffer emailed with another staffer: "UGH! We have all kinds of planes, trains and automobiles manifests to now scramble with."

At the time, Interior spokeswoman Heather Swift told CNN that Lola Zinke extended her trip because she was asked to participate in a Rolling Thunder ride and ceremony, and that she paid for her own commercial flight returning from Alaska.

Zinke's travel has most recently been in the spotlight over a two-week vacation to Greece and Turkey last year on which the Secretary and his wife traveled with a security detail, as first reported by Politico.

"Love on the Bosporus #summer," Lola Zinke wrote in an August 2017 tweet with a photo of herself and Secretary Zinke, the sun glinting across the water behind them. One reply to the tweet suggested that she shouldn't have posted it while "everyone's dear lands" were "on the chopping block." Another said that the trip was "unnecessary and costly," and that the Zinkes should have paid for it themselves.

Lola Zinke replied, "Linda dear, that was our 25th wedding anniversary trip, not that it's any of your business. You did not pay one cent. Cheers."