Yet the South Bend, Indiana, mayor now faces cascading questions he has been unable to answer about his work at McKinsey & Co., the management consulting firm that accounts for the entirety of his private-sector career. He hasn’t revealed his clients, citing a nondisclosure agreement he signed at the outset of his employment.

The three years Buttigieg spent at McKinsey represent one-fifth of his professional resume. His campaign on Friday night for the first time disclosed broad strokes beyond the most elemental details of his work, some of which he also discussed in his memoir, which was published in February.

The pressure to disclose more about his work at McKinsey comes as the 37-year-old mayor also faces increased scrutiny about his lack of appeal to African-American voters, and amid increasing calls from Sen. Elizabeth Warren of Massachusetts, who does not hold closed-door fundraising events, to reveal details about his campaign’s fundraising operation — including the names of his bundlers.

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“This is about the conflicts that he is creating every single day right now,” Warren told reporters Saturday in New Hampshire.

For his part, Buttigieg has called on Warren to release more than the 11 years of personal tax returns she has already disclosed. Warren released a list of more than 50 legal clients in May.

All of this comes as Buttigieg has established himself as the front-runner in Iowa, where Democrats hold the first-in-the-nation nominating caucuses Feb. 3. Democrats here are increasingly focused on selecting a candidate who will be the strongest in a general election against President Donald Trump, who has refused to release any of his tax returns and did not divest himself from businesses that profit from his administration and campaign.

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The pressure on Buttigieg to reveal more about his work at McKinsey is coming not only from his 2020 rivals like Warren, who in recent days has become far more aggressive in her attacks on him, but also from other Democratic politicians.

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On Friday night in Waterloo, Iowa, Mayor Lori Lightfoot of Chicago, who had spoken favorably of Buttigieg just weeks earlier, told Buttigieg during an onstage interview that he should reveal for whom he did work at McKinsey.

“You said you can’t talk about your work at McKinsey because of a nondisclosure agreement, and I think you said today you’ve got to honor your commitment to McKinsey,” said Lightfoot, a corporate lawyer herself. “I’m asking you, should you break that NDA so you have the moral authority and the high ground against somebody like Trump, who hides behind the lack of transparency to justify everything that he’s doing?”

Buttigieg first tried to dodge the question from Lightfoot, quipping that it was his first job out of school and it was “not like I was the CEO.”

He added: “I pushed as much information as I can, without breaking the promise that I made in writing. And I am asking my former employer to do the right thing, to not make me choose between claiming the moral high ground and going back on my word.”

Buttigieg told reporters later that he would not unilaterally break the nondisclosure agreement with his former employer.

“It’s important to me to keep my word, and it’s also very important to me to offer as much transparency as possible,” he said. “I’m squaring that circle the best I can by pushing out the information that we did.”

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The McKinsey question has hung over Buttigieg as he has grown into a more formidable presidential candidate. In June his campaign first asked McKinsey which details of his work there could be revealed. In September he told reporters aboard his campaign bus that his McKinsey tenure wasn’t “something that I think is essential in my story,” though when he ran for office in Indiana in 2010 he used his McKinsey experience as evidence of his grasp on private-sector economics.

In recent days, as scrutiny of his work with the firm reached new heights following revelations McKinsey helped the Trump administration carry out its immigration policies, Buttigieg himself publicly requested to be released from his nondisclosure agreement.

And on Friday night the campaign released its most detailed timeline yet of his work for the firm, laying out details of the type of work he performed but not revealing the names of his clients.

While Buttigieg’s rivals spent Friday and Saturday salivating online over his McKinsey ties, there was little evidence the story had broken through yet in Iowa.

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“It’s the first I heard of it and I just don’t see the importance of it right now,” said Lon Gingerich Feil, who came to see Buttigieg Saturday in Mt. Vernon. She added: “I don’t believe that anybody’s completely blameless in anything as far as politics goes.”

Buttigieg’s political allies insist that anger over his McKinsey tenure is manufactured by his political opponents and is not widely shared among early-state Democrats.

“He answers the questions about it with the fact it was a first-time job,” said Laura Hubka, the Democratic Party chairwoman in Howard County, Iowa, who has endorsed Buttigieg. “Every attack on Pete is making him look more attractive to middle-of-the-road voters.”

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And the Buttigieg campaign has not shifted into crisis mode over the McKinsey story. Rep. Don Beyer of Virginia, the first member of Congress to endorse Buttigieg, said the campaign had not circulated any talking points about the mayor’s McKinsey tenure.

“I think he’s got a perfectly clear explanation, which is that he signed a nondisclosure agreement and McKinsey is famously secretive,” Beyer said Saturday.

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Yet Buttigieg’s handling of calls to name his McKinsey clients echoes the most politically damaging episode of his years as mayor: the city’s withholding of secret recordings of police officers that led Buttigieg to demote a black police chief.

The mayor removed the chief in 2012, he has long said, after learning that the FBI was investigating the chief for violating wiretap laws. But Buttigieg declined to release the tapes, citing federal privacy laws as he fought a subpoena for the tapes from the City Council. In South Bend, reports and rumors have circulated for years that the tapes include white officers using racist language and describing illegal activity.

Buttigieg has admitted that his initial response to the crisis was overly legalistic. He failed to understand that his actions sent a broader message that reinforced black residents’ distrust of the police.

(Today, the mayor himself calls for the tapes’ release, though their fate is tied up in court, with the police officers heard on the recordings fighting disclosure.)

In the case of Buttigieg’s McKinsey clients, he may be similarly at risk of offering an overly legalistic defense of nondisclosure, while misjudging the deep suspicions that liberal voters harbor for corporate influence on politics.

Buttigieg’s appeal to many voters is his rejection of a lucrative private-sector career to enter public service; part of his good government credo has long been greater transparency in the city he runs. He first ran for municipal office in 2011 promising a breakthrough in the city’s transparency. In many ways he delivered. The city now uploads online data on police use of force and complaints against officers, vacant and abandoned properties, and many details of city spending. In 2017 the mayor and his staff celebrated fulfilling 10,000 requests under Indiana’s open records law.

Another transparency effort, a $1.5 million purchase of body cameras for police officers, ended up at the center of a political crisis for the mayor this summer. A white officer failed to activate his camera during an encounter in which he fatally shot a black man in downtown South Bend, sending the city, and Buttigieg’s campaign, into turmoil. Buttigieg suspended campaigning to face angry and anguished residents. The narrative of distrust of the police was projected on the national stage.

Buttigieg has emerged as perhaps the most polarizing figure among Democratic insiders.

He is the subject of the most open contempt among his rivals, a feeling that often extends to their supporters.

Kim Miller, a Warren backer who works for the teachers union in Cedar Rapids, Iowa, said Monday after a Warren event at the University of Iowa that Buttigieg’s resume — Harvard, McKinsey, Navy veteran, small-town mayor — was not sufficient to make him the Democratic standard-bearer.

“What qualifies him to even run? It’s pretty presumptuous,” Miller said. “It’s amazing that he’s taken off. Iowans are weird.”

This article originally appeared in The New York Times .