Sen. Elizabeth Warren’s "wine cave" attack on fellow top-tier Democratic nomination rival Pete Buttigieg grabbed headlines and became the most memorable moment out of last week’s debate.

But the aftermath of the jab over the South Bend mayor’s ritzy Napa fundraiser also illustrates how her escalating feud with Buttigieg has opened her up to charges of hypocrisy. Buttigieg, on stage, pointed to the Massachusetts senator's own past fundraising in arguing she’s imposing “purity tests” she can’t pass. Critics later seized on a Senate re-election fundraiser she held at a winery in Boston a year-and-a-half-ago -- though her campaign rejected the comparison.

WARREN CALLED OUT OVER PAST FUNDRAISER AT WINERY

Warren’s public pressure over Buttigieg’s consulting work has created a similar conundrum.

As the populist, progressive senator successfully pushed for Buttigieg to release a list of clients from his McKinsey days, he, in turn, applied pressure over the senator’s past legal work in the private sector. That helped spur her own disclosures that she made nearly $2 million in consulting for corporations and financial firms during her years as a law professor at such prestigious schools as Harvard University and the University of Pennsylvania.

And while she pushed Buttigieg toward transparency by arguing any potential “conflicts of interest” should be out in the open, Warren has done additional advising work apparently not highlighted by the campaign. Court documents reviewed by Fox News reveal that Warren advised numerous foreign countries on bankruptcy reform during her years as a law professor.

“I have served as an American Adviser to the German Government Task Force on Bankruptcy Reform,” Warren wrote in a legal document submitted in the case Bolin v. Sears, Roebuck & Co., where she served as an expert witness nearly two decades ago.

Warren went on to note in the court document detailing her background that she had agreed to “advise the Norwegian Government on proposed consumer and business bankruptcy reforms” and “I have also served as an informal adviser to other governments considering bankruptcy reform in Latin America, Europe, and Asia.”

The case is listed on Warren’s presidential campaign website, in the section highlighting her past legal work. But the paragraphs where she spotlights her past work on behalf of foreign governments are not mentioned.

As the campaign website explains, Warren earned nearly $100,000 while serving as an expert witness in the consumer class-action lawsuit against Sears “over its aggressive debt collection practices….Elizabeth served as an expert witness who testified that Sears’ debt collection practices violated bankruptcy laws. The parties ultimately settled.”

Asked by Fox News about the foreign government advising, Warren spokesman Chris Hayden described this as unpaid work.

"Elizabeth was the nation's leading expert in bankruptcy and was active in the debate over bankruptcy reform in the United States. As an expert, she occasionally provided advice to other countries looking to make changes to their bankruptcy laws. To our knowledge, she was not paid to provide any of this advice," he said in a statement Tuesday.

There's no indication that Warren's advising work, including for foreign governments, was problematic. But the senator's deep history of consulting work, as well as her own history of fundraising for her Senate campaigns, has created a challenge as she casts Buttigieg as secretive on those fronts. The Washington Examiner reported recently that Warren, while raising questions about Buttigieg's McKinsey work, once was involved in hiring the same firm years ago at Harvard.

The Warren campaign in May made public a list of nearly 60 cases – dating back more than 30 years – where the candidate had performed legal work. Earlier this month, the campaign updated the website with new data and information on Warren’s past legal work.

The new list included what Warren campaign spokesperson Kirsten Orthman said was “all the income she earned from each case that we have been able to determine from public records, Elizabeth’s personal records and other sources.”

The move by Warren came after days of repeated attacks by the Buttigieg campaign, which had been relentlessly urging Warren to release her tax returns from before 2008, to give full transparency to the legal work she did for corporate clients similar to the giant corporations she now rails against as she runs for the White House.

HOLDING BACK NO MORE, WARREN TAKES AIM AT TOP 2020 RIVALS

At the same time, Warren was hammering Buttigieg over his three-year tenure at consulting firm McKinsey & Company. The firm has been criticized recently for its past work with U.S. Immigration and Customs Enforcement (ICE), authoritarian governments and opioid manufacturers.

Under attack from Warren, Buttigieg released new details on his confidential work at McKinsey. And he reiterated his calls for the consulting firm to release him from a nondisclosure agreement. A few days later McKinsey gave Buttigieg permission to release the names of the clients he served during his tenure with the firm.

The fireworks between the two candidates in December came as Warren saw her poll numbers deteriorate over the past two months in national surveys and -- more importantly -- in polls in Iowa and New Hampshire, the first two states to hold contests in the primary and caucus presidential nominating calendar. At the same time, Buttigieg – the longest of long-shots when he launched his campaign – surged to top-tier status in polling in Iowa and New Hampshire.

Warren’s also pummeled Buttigieg over his closed-door, top-dollar fundraisers.

Unlike former Vice President Joe Biden, Buttigieg wasn’t opening his fundraisers to press coverage. While her aggressive jabs at Buttigieg were a departure from her past general avoidance of criticizing rivals, attacking corruption in government has been a core message of Warren’s campaign dating back to the launch of her White House bid at the beginning of the year.

"We have other candidates who have decided to finance their campaigns by doing closed-door fundraisers, sucking up to the corporate executives, the millionaires, the billionaires," she told the crowd at a town hall in Charleston, S.C. earlier this month, as she targeted Buttigieg.

Warren's full-court press was successful, as Buttigieg aides eventually announced that the candidate would open fundraisers to reporters and release the names of people raising money for their campaign.

WARREN, BUTTIGIEG, TRADE SHOTS OVER FUNDRAISING, WINE CAVES

Warren then took her fundraising attacks to prime time, as the two tangled at last week’s Democratic presidential primary debate in Los Angeles.

As the two faced off on the debate stage, Warren highlighted that Buttigieg recently held a fundraiser “that was held in a wine cave full of crystals and served $900 a bottle wine.”

“Billionaires in wine caves should not pick the next president of the United States,” she stressed.

Firing back, Buttigieg said “I’m literally the only person on this stage who’s not a millionaire or a billionaire."

"This is the problem with issuing purity tests you cannot yourself pass,” Buttigieg added. “Senator, your net worth is 100 times mine.”

“I do not sell access to my time,” Warren responded. “I don’t meet behind closed doors with big-dollar donors.”

Buttigieg counter-attacked, noting that Warren transferred millions of dollars to her presidential campaign that she initially raised at big-bucks fundraisers during her 2018 Senate re-election bid.

“Your presidential campaign right now, as we speak, is funded in part by money you transferred having raised it at those exact same big-ticket fundraisers you now denounce,” Buttigieg stated. “Did it corrupt you, senator? Of course not.”

After the debate, the AP reported that Warren held a fundraiser in June 2018 – as she successfully ran for re-election for a second term in the Senate – at the City Winery Boston. Donors attending the event were entertained by Grammy-winning singer Melissa Etheridge and for those contributing big bucks, there was a VIP photo reception and premium seating as well as souvenir wine bottles – practices Warren attacked Buttigieg over during last week's debate.

Warren’s campaign, responding to the report, noted that “this event, which occurred before the Presidential campaign, was held at a large public music venue with multiple locations throughout the country, not an exclusive wine cave. Their most expensive bottle of wine is $49. As the invite shows, the minimum to get in was $100. It did not require a maxout donation to attend.”

Pushing back against charges she was being hypocritical, Warren explained that she “saw how the system worked” when she held top-dollar fundraisers she now rails against – and decided that as she runs for the White House she’s “going to do better than that.”

"I have been here almost a year now, and I have sold no access to my time. I have made no special calls to rich people. I haven't had a single fundraiser behind closed doors," Warren said Saturday while campaigning in Iowa. "I want to move the system in a better direction, not in a worse direction."

Despite being forced to explain potential inconsistencies on these fronts, Warren has nevertheless enjoyed a burst of attention over the "wine-cave" attack -- and put Buttigieg on his heels, opening him up to additional scrutiny as well.

Axios reported on Sunday that a top Buttiegieg fundraiser reportedly sent to a prospective donor an email saying “if you want to get on the campaign’s radar now…you can use the link below for donations.”

The prospective donor told Axios that the email was “very telling and concerning.” The fundraiser – H.K. Park – is listed on the Buttigieg website as someone who’s raised at least $25,000 for the campaign.

The report of the unusually blunt suggestion could be a rare look at a campaign possibly offering potential donors a way to buy influence with the candidate.

The Buttigieg campaign, though, said the email did not come from them and they did not authorize the language in it.