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Despite employee turnover that perennially ranks near the highest in the Senate, Ms. Klobuchar has defenders among her former staff. She noted at the forum that some people had been with her for many years.

Erikka Knuti, a former communications aide to the senator, described her experience as broadly positive and said Ms. Klobuchar could be contrite at times, remembering a gesture of regret from the senator once after she snapped at Ms. Knuti in an elevator in front of another lawmaker. “That wasn’t O.K.,” she recalled Ms. Klobuchar telling her. “It made me feel valued,” Ms. Knuti said.

While there was wide consensus in the interviews that women were often held to a different standard as bosses, former aides — female and male — said their concerns about Ms. Klobuchar’s behavior should not be dismissed as gender bias. Many of the aides said they had worked for both men and women, for lawmakers both compassionate and unkind, without encountering anyone else like Ms. Klobuchar.

The world of congressional staffs is one of long hours and low pay, with much of the work shouldered by twentysomething junior aides who are learning on the job. Some members of Congress are notorious for round-the-clock phone calls, late-night email and fierce attention to their own press coverage. Ms. Klobuchar is among them, but former aides said they were especially troubled by her willingness — in excess of other senators’, they said — to embarrass staff members over minor missteps or with odd requests.

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Most of those interviewed for this article — describing memories that span from shortly after her election in 2006 to the much more recent past — discussed their time with Ms. Klobuchar on the condition of anonymity for fear of reprisal from the senator. These concerns were not idle, they said. Saving potentially damaging emails from Ms. Klobuchar became something of a last-day ritual, the aides said, in case they ever needed evidence of her conduct for their own reputational protection.