At least three people have withdrawn from consideration to lead Sen. Amy Klobuchar’s nascent 2020 presidential campaign — and done so in part because of the Minnesota Democrat’s history of mistreating her staff, HuffPost has learned.

Klobuchar, who plans to make an announcement about a potential presidential bid on Sunday in Minneapolis, has spent the past several months positioning herself to run for president. She’s beloved in her state as a smart, funny and personable lawmaker and has gained national attention for her lines of questioning at high-profile hearings.

But some former Klobuchar staffers, all of whom spoke to HuffPost on condition of anonymity, describe Klobuchar as habitually demeaning and prone to bursts of cruelty that make it difficult to work in her office for long.

It is common for staff to wake up to multiple emails from Klobuchar characterizing one’s work as “the worst” briefing or press release she’d seen in her decades of public service, according to two former aides and emails seen by HuffPost.

Although some staffers grew inured to her constant put-downs (“It’s always ‘the worst,’” one said sarcastically, “‘It was ‘the worst’ one two weeks ago”), others found it grinding and demoralizing. Adding to the humiliation, Klobuchar often cc’d large groups of staffers who weren’t working on the topic at hand, giving the emails the effect of a public flogging.

“Senator Klobuchar loves her staff ― they are the reason she has gotten to where she is today,” a campaign spokesperson told HuffPost. “She has many staff who have been with her for years ― including her Chief of Staff and her State Director, who have worked for her for 5 and 7 years respectively ― and many who have gone on to do amazing things, from working in the Obama Administration (over 20 of them) to running for office to even serving as the Agriculture Commissioner for Minnesota. She is proud of them and the work they have done for Minnesota.”

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Some people who worked for Klobuchar say they valued the experience: Klobuchar has an unrivaled command of details, puts in long, enthusiastic hours, and simply demands that her office meet those same high standards, several former staffers maintained. Those employees described working for her as a challenge, but an exhilarating one that caused them to grow and perform their best work. They question whether former co-workers who thought she was abusive were falling for sexist stereotypes about female leaders with high standards.

Some former staffers of Sen. Amy Klobuchar describe the lawmaker as habitually demeaning and prone to bursts of cruelty that make it difficult to work in her office for long. (Photo: ASSOCIATED PRESS)

Reached for comment, Klobuchar’s office referred HuffPost to multiple ex-staffers who shared glowing statements about working for her.

“I’ve heard people say she’s tough to work for and I sometimes cringe when I hear it because I rarely hear that said about male bosses in Congress despite the fact that half of Congress is tough to work for,” said Tristan Brown, a former legislative aide who called Klobuchar “probably the most brilliant, hardworking person I’ve had the privilege to work for.”

Erik Garcia Luna, who worked in Klobuchar’s Minneapolis office from 2009 to 2014, remembers her as kind. He said that she called her staffers during the 2013 government shutdown to check in with them and make sure they and their families were taken care of.

He said he had no idea why there were such divergent views from people who had worked for the senator: “I don’t know what to make of them, to be frank.”

Do you have more information on what it’s like to work for Sen. Klobuchar — or other members of Congress? Get in touch: scoops@huffpost.com

What is indisputable, however, is that Klobuchar’s office consistently has one of the highest rates of staff turnover in the Senate. Klobuchar’s rate of turnover ranked No. 1 in an analysis of all Senate staff salaries between 2001 and 2016, conducted by LegiStorm, a widely used database of congressional staff salaries. (Klobuchar was sworn into office in 2007.) She’s now third, behind Maryland Democrat Chris Van Hollen and Louisiana Republican John Kennedy.

And this is not the first time Klobuchar has had issues building a team because of worries about her mistreatment of staff.

A former employee in her Senate office recalled her struggling to find an outside candidate to replace an outgoing chief of staff. A staffer in another Hill office recounted losing interest in a job opening with Klobuchar when a current staffer, the one conducting the interview, conveyed that avoiding Klobuchar’s anger was a significant part of the job.

The senator has acknowledged she has “high expectations,” but many people who have worked with Klobuchar or interacted with her and her staff say her treatment of staff goes beyond the normal expectations of excelling in a job.

Three former staffers said Klobuchar has tasked them or their co-workers with performing personal errands, such as making her personal appointments, washing dishes at her home or picking up her dry cleaning.

Senate staff are generally prohibited by Senate ethics rules from performing personal duties for members.

However, the practice is also common on Capitol Hill. A former staffer who was never aware of Klobuchar tasking a staffer with personal chores said many lawmakers make such requests. “The honest truth to this is, there are a lot of people [in Congress] who really take advantage of office staff,” the former staffer said.

In egregious cases, members of the House of Representatives who violated rules against personal use of staff have been subject to ethics investigations.

The reality of working for Klobuchar is at odds with the Midwestern-nice image she has cultivated in public: an unflappable workhorse and “the senator next door,” which was the title of her 2015 memoir.

One morning several years ago, when most of the office staff was running late — the ex-staffer couldn’t remember the reason — Klobuchar wrote out tardy slips and placed them on each missing aide’s desk. The staffer recalls incredulous bursts of laughter as her co-workers arrived one by one to find the notes, but Klobuchar was deadly serious. An aide whom she called into her office walked back out in tears.

“She was constantly lighting new fires,” a former staffer said, sometimes at the expense of focusing on legislative work.

“When you have people who don’t want to work for you, you can’t be as effective,” the staffer added.

Kevin Robillard contributed reporting. This story has been updated to include more details about the Senate staff turnover rankings conducted by LegiStorm.

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This article originally appeared on HuffPost.