The menacing posts began cropping up on Twitter last September just hours after a former aide to Gov. Andrew M. Cuomo of New York sued him over sexual harassment claims.

The tweets attacked the aide, Charlotte Bennett, in starkly personal terms. “Your life will be dissected like a frog in a HS science class,” read one of the most threatening, which also featured a photo of Ms. Bennett dancing at a bar in lingerie.

The post was part of a thread written by Anna Vavare, a leader of a small but devoted group of mostly older women who banded together online to defend Mr. Cuomo from a cascade of sexual misconduct claims that led to his resignation in August 2021. But it turns out, her tweets had secretly been ordered up by someone even closer to the former governor’s cause: Madeline Cuomo, his sister.

In the hours before the posts went live that morning, Ms. Cuomo exchanged dozens of text messages with Ms. Vavare and another leader of the pro-Cuomo group We Decide New York, Inc., pushing the activists to target Ms. Bennett, one of the first women to accuse Mr. Cuomo of sexual harassment. She appeared to invoke her brother’s wishes.

“Good Morning Just spoke and he thinks a distraction could be helpful today,” Ms. Cuomo wrote in the private texts reviewed by The New York Times. She suggested posting “photos of Charlotte In her sex kitten straddle” taken from Ms. Bennett’s Instagram account, potentially alongside more “austere, professional” ones of loyal Cuomo aides.

“No respectable woman would EVER pose like that,” Ms. Cuomo added.

She went on: “Bimbo photos.” “Really despicable.” “Unsophisticated girls.”

Far from an isolated episode, the unvarnished exchange is part of a trove of more than 4,000 text messages, emails and voice memos between leaders of the group and Ms. Cuomo shared with The Times this summer. Together, they provide unusual insight into how far members of one of America’s most storied political families were willing to go to rehabilitate a fallen Democratic scion and humiliate those they believed had wronged him.

Made up almost entirely of women inspired by Mr. Cuomo’s handling of the Covid pandemic, We Decide New York rapidly joined forces in spring 2021 to defend an increasingly isolated governor as traditional allies abandoned him. The group swarmed his critics on social media, sold Cuomo swag and pushed for due process.

But four of the group’s current leaders said in interviews that even as their work appeared organic to the outside world, Ms. Cuomo, 58, began privately exerting control. Starting just weeks after the group was formed, she steered its volunteer activists — many in their 50s, 60s and 70s — to prop up her brother and hound his accusers ever more aggressively.

It is unclear how much Mr. Cuomo knew about his sister’s efforts. He does not appear to have directly communicated with the supporters. But in the messages reviewed by The Times, some of them sprinkled with typos, Ms. Cuomo repeatedly stated that she was keeping her brother updated and acting at his direction.

“I just hung up w A again and he wants you both to know how much he appreciates ALL your hard work,” Ms. Cuomo wrote last September. A few days later: “He’s seeing everything.”

Ms. Cuomo made a point of highlighting her brother’s interest and appreciation in the group’s efforts, as seen in this group text sent on Sept. 5, 2022.

Madeline Cuomo

I just hung up w A again and he wants you both to know how much he appreciates ALL your hard work,
and your willingness to get this out today
on LABOR DAY of all days!!!!!

You ladies share the same work ethic.
I believe we were all raised quite similarly
which accounts for our
like-minded sensibilities

Sandy Behan

Tell him I couldn’t think of a better way to spend the holiday. We are there for your always whatever you need.?😘💙

Madeline Cuomo

We all wish we didn’t have to go negative ever
but it’s clear they’re never going to stop and leave us alone to do GOOD WORK until THEIR truth is exposed.

Ms. Cuomo was adamant her role be hidden. She repeatedly asked her interlocutors to delete messages. And when a reporter for The Times called some leaders of the group for an earlier article, Ms. Cuomo instructed the women to falsely claim they had no contact with the Cuomos, according to Sandy Behan, the founding president of We Decide.

Ms. Cuomo, in a statement on Monday, acknowledged her involvement with the group, saying she was focused on “protecting my family” but insisted that her brother played no role.

“I acted on my own with the women of WDNY, without his involvement in any way,” she said. Several hours after the article’s publication, she amended her statement to say she had only invoked her brother’s name so the women “felt their efforts were appreciated.”

Mr. Cuomo’s spokesman, Rich Azzopardi, also sought to distance the governor from his sister’s efforts.

“The governor does not personally have nor does he follow social media accounts, and he was not directly or indirectly involved in these online efforts,” he said. “When he’s had something to say, he has not held back from doing so publicly.”

Ms. Behan, 71, said she and others were awe-struck after being contacted by Ms. Cuomo and were eager to help her with what they believed was a shared — if sometimes unsavory — mission. But by late last year, the relationship had imploded around a proposed documentary project and Ms. Cuomo’s intensifying demands.

Ms. Behan said the bitter recriminations nearly destroyed her group and its reputation. It also shook her confidence in the Cuomo family she had once revered.

“Madeline was demanding. She wanted to make sure we toed the line, and we did,” she said. “This was a means for her to get information out to benefit her brother. She didn’t want to be my girlfriend — she was using us.”

‘It’s not that I’m doing anything wrong’

From the first days she reached out in May 2021, when Andrew Cuomo still hoped he could fend off his accusers and stay in office, Madeline Cuomo made clear she knew the potential value of what she was doing — and the peril.

A lawyer and the youngest daughter of former Gov. Mario Cuomo, Ms. Cuomo had spent her life in political circles quietly supporting the political ambitions of her more famous family members and wanted to keep it that way. “Family has always been the most important thing in my life,” she told The Times for a 1993 Vows column.

But the legal jeopardy surrounding her brother made her preference for discretion even more critical. Chris Cuomo, the youngest sibling, lost his job as an anchor at CNN after the extent of his involvement in the governor’s affairs became public.

“It’s not that I’m doing anything wrong,” Ms. Cuomo wrote to Ms. Behan in June 2021, just weeks into their correspondence. “This has all been exasperatingly unfair. But anything we are associated with will lose efficacy because they will say we put you up to it.”

The messages show that Ms. Cuomo went on to propose that she could feed information and advice to We Decide New York so its dozens of members could call out “one-sided” media accounts and dig into “the facts” about accusers like Ms. Bennett, who said the governor asked intrusive questions about her sex life, and Lindsey Boylan, the first former aide to accuse Mr. Cuomo of sexual harassment.

Ms. Behan, a retired advertising executive from Rochester, N.Y., was giddy in those early days. Like other ardent Cuomo supporters, she had formed a deep loyalty to the governor during the darkest days of the pandemic, when his daily news conferences were appointment viewing. Now, they suspected he was being railroaded.

“I just talked to the Madeline Cuomo,” Ms. Behan remembered telling her husband in disbelief when the women first connected. “My first thought was she is going to help us grow this organization, help us do what we want to do for the governor.”

In her statement on Monday, Ms. Cuomo said that she initially contacted the group to urge members not to make “ill-advised” attacks on the governor’s accusers in his name. “I explained to them that there was a difference between calling into question a person’s credibility and attacking them publicly,” she said.

Ms. Behan disputed that account, and produced text messages showing Ms. Cuomo introducing herself and then demanding that Ms. Behan remove a journalist from another pro-Cuomo Facebook group that she helped moderate.

Still, the tone was amicable at first. Though Ms. Cuomo took no formal role in the group, she fed talking points when reporters came calling and quietly helped coordinate a sparsely attended rally for her brother in the days before he quit, even signing off on poster designs. “Please advise as to what you want us to do ASAP,” Ms. Behan texted Ms. Cuomo on the eve of Mr. Cuomo’s resignation announcement.

After Mr. Cuomo resigned, the women were lost. When they asked Ms. Cuomo for “some direction” to keep up the cause, she could offer none at first. But as summer of 2021 turned to fall, she took a keen interest in the group’s work soliciting voters’ views about what happened to Mr. Cuomo, and soon began communicating regularly about a growing effort to rehabilitate his image.

By March 2022, Mr. Cuomo was publicly toying with a comeback bid, taking out television ads declaring himself exonerated, granting occasional media interviews and speaking publicly about “cancel culture.” Ms. Cuomo put We Decide New York on notice for a possible campaign and asked Ms. Behan to help line up women who could build a groundswell.

The monthslong grind even wore on Ms. Cuomo, who confided in early March that her brother was “very difficult to work with.”

“He also never admits vulnerability or expresses gratitude — or at least very rarely do you see that side of Andrew,” she wrote in an email from her AOL account. “This nightmare has not only affected him but rather my entire family, and it would be nice to hear him say he gets it.”

In May, as chances of Mr. Cuomo running faded, their focus turned to undermining his former lieutenant, Gov. Kathy Hochul, who had succeeded him. Ms. Cuomo, who clearly loathed Ms. Hochul, helped coordinate a meeting between Ms. Behan and Representative Tom Suozzi, a Democrat challenging the new governor.

Days later, she encouraged Ms. Behan to sharpen her criticisms of Ms. Hochul in a letter that We Decide New York was drafting to chastise Hazel Dukes, the head of the New York State N.A.A.C.P., for backing Ms. Hochul.

Ms. Cuomo suggested adding “something to the effect of: From the time KH feebly took the reigns she has steered this ship out of control.” The critique went on, with Ms. Cuomo accusing Ms. Hochul of “selectively coveting his accomplishments as her own.”

When Chris Cuomo filed an arbitration demand against CNN that spring, his sister asked the group to buck him up, too. “Let’s show some love,” she wrote.

A heroic photo of Chris Cuomo quickly appeared on the group’s Twitter page, along with a hashtag: #BringBackChrisCuomo.

‘Andrew is asking’

By last August, Ms. Cuomo had refocused on her brother’s accusers, sometimes sending dozens of texts and voice memos a day with marching orders that veered beyond fact-based defenses.

“KH and LB need to be frightened into shutting up right now — Enough is enough,” she wrote in August, referring to Ms. Boylan and Karen Hinton, a Democratic public relations specialist who once worked for Mr. Cuomo in Washington in the Clinton administration. .

The uptick in activity seemed tied as much to Mr. Cuomo’s evolving career prospects as to the lawsuit brought by Ms. Bennett. Ms. Cuomo told Ms. Behan that he would soon be launching a new podcast, and his accusers “need to know now that they can’t be attacking when he comes out.”

She appeared particularly preoccupied by Ms. Hinton, who accused Mr. Cuomo of initiating an unsolicited “intimate embrace” in a hotel room decades earlier, before he was governor. In an August email, Ms. Cuomo wrote that Ms. Hinton and Ms. Boylan were hypocritical to complain about inappropriate workplace behavior given episodes she claimed happened in their own lives. “PLEASE,” she added.

She followed up the next day warning her correspondents, “Please delete and don’t share — Put in your own words first,” then persisted days later in knocking Ms. Hinton, this time in a list-like text.

“Unauthentic

Uninspired

Unkind

Ugly motives

Underhanded

Gender descriminatong

Home wrecker

Basically,

Uuuuuuugh.”

The group posted to its Twitter page a few hours later repeating most of the text as if it was its own, and produced a video splicing clips of Ms. Hinton to make her look untrustworthy.

At one point, Ms. Cuomo requested a post focusing on Ms. Hinton’s husband’s departure from the Cuomo administration, adding, “Andrew is asking.”

Ms. Behan and Valerie Skarbek, another We Decide New York co-founder from Illinois, said they could never be certain the extent to which Mr. Cuomo — who was notorious for micromanaging his public image — was involved in his sister’s requests. But the group usually complied.

Ms. Cuomo even discussed possible attack lines against an unnamed state trooper who accused Mr. Cuomo of having touched her inappropriately when she was a member of his protective detail.

“I think we should use current sentiment around police and authority in our favor” to undercut the trooper’s credibility, Ms. Cuomo wrote by email. “Her motivations need to be considered as well. This is a woman with real financial insecurity.”

Ms. Cuomo strategized how to attack the credibility of a state trooper whose accusation of Mr. Cuomo touching her inappropriately led to a lawsuit.

From: Madeline Cuomo
Subject: Re:
Date: August 30, 2022 at 11:24 AM

…
I think we should use current sentiment around police and authority in our favor and reply by saying something to the effect that her being a member of the force does not in any way mean she is infallible, and her motivations need to be considered as well.

This is a woman with real financial insecurity. I believe her husband’s out of work— and she had other expenses and needs the money. (easy enough to google articles)
…

Ms. Bennett’s lawyer, Debra Katz, called Ms. Cuomo’s role “shocking but not surprising” and said she would seek to depose her and other potential witnesses in her client’s lawsuit against the former governor.

“The governor clearly relied on family members and friends to try to smear and intimidate women who came forward,” she said, adding that the photo of Ms. Bennett in lingerie was taken at a private party where guests were urged: “Come as your most outrageous self!”

The tactics began to make Ms. Behan uneasy. “Even a slut has right to not be sexually harassed,” she wrote by text the September morning Ms. Cuomo wanted to circulate photos of Ms. Bennett online after she filed suit.

Ms. Cuomo suggested workarounds, but by then a rift had already begun to open that would swiftly turn the longtime allies into bitter enemies.

‘Without me, there would have been no we’

The first, imperceptible fissures had started forming months earlier, when a filmmaker, Adam Friedman, approached We Decide New York for help raising money for a feature-length documentary on Mr. Cuomo.

Ms. Behan and her board loved the idea, and the group began pouring dozens of hours a week into the project, which they hoped would help Mr. Cuomo tell his side of the story. Ms. Behan thought she also had the blessing of Ms. Cuomo, who edited fund-raising letters for the film project and coached the women through interactions with the governor’s team, records show.

But by last fall, Ms. Behan and several of her board members began to fear that the Cuomos were toying with them. The governor’s top aides demanded to see budgets, won guarantees of editorial oversight and, after extensive nagging, agreed Mr. Cuomo would sit for an interview — but then never actually made the former governor available.

Frustration boiled over last September, and the response was unsettling. Florence Jones, a Sept. 11 survivor on We Decide New York’s board from Long Island, sounded off on Ms. Cuomo by email, telling her to allow “A GROWN MAN” to “HANDLE THIS W/O HIS SISTER BEING INVOLVED.”

Ms. Cuomo was livid, demanding an apology — or else she would cut off the group and the film it was so invested in. “Whether she likes it or not,” Ms. Cuomo told Ms. Behan in a voice memo, “without me, there would have been no we.”

To Ms. Behan, the behavior felt like bullying, and the pattern repeated itself when Ms. Vavare unexpectedly resigned from We Decide New York’s leadership team, citing exhaustion and a dust-up over who controlled passwords to the group’s social media accounts. Ms. Behan said she was blindsided by the decision, but Ms. Cuomo blamed her and sent repeated messages insisting that she bring Ms. Vavare, who lived in Canada, back into the fold or lose her patron.

Ms. Behan and allies like Ms. Skarbek and Christine Fritz, 60, said they labored for weeks to appease Ms. Cuomo. When Ms. Behan’s family members fell ill with Covid and Ms. Behan said she would have to temporarily step away, Ms. Cuomo told her “Covid is not what it was” and moved to cut off the documentary.

Things rapidly unraveled. The board accepted Ms. Vavare’s resignation. Mr. Friedman was so fed up he confided in the women that he was contemplating suing the Cuomos. Then Ms. Cuomo found out and proceeded to trash the filmmaker and Ms. Behan directly to their members, accusing the pair of shady financial dealings and inappropriately pocketing documentary money.

Former friends, including Ms. Vavare, began to demand donations back and used social media to repeat increasingly twisted versions of Ms. Cuomo’s claims. When Ms. Behan tried to defend herself and disprove the statements as recently as May, Ms. Cuomo warned her by text not to do something “you will have to pay for deeply.” And while the group did eventually threaten legal action, it could not afford to follow through.

Both Mr. Azzopardi and Ms. Cuomo acknowledged that the former governor had been made aware of the group’s documentary project, but had decided not to pursue it. Ms. Cuomo said it was the “only time I discussed the organization with him.”

It all took a toll: Ms. Behan said she developed shingles from stress; Ms. Jones, 62, said her hair began falling out. Their group all but collapsed.

Ms. Behan said the experience also forced her to re-evaluate. She conceded she had been naïve about the documentary project, but maintains she had made nothing off it, sharing bank records to back up her claim. She said she “made assumptions that may not have been accurate” about Mr. Cuomo’s accusers, too, and believes that her real transgression came when she stopped meeting Ms. Cuomo’s demands.

“We were victims in this thing. We were derailed by Madeline,” she said. “I do feel bad about not getting people their money back, but it was out of our control.”

Ms. Vavare did not respond to requests for comment.

Mr. Friedman, who was paid $50,000 raised by We Decide New York for his preliminary work, declined to comment.

For her part, Ms. Skarbek, 49, said that close contact with the Cuomos had rearranged her views on the man she set out to fight for.

“It’s amazing to me how I saw Gov. Cuomo when I started this organization and how I see him now and judge his innocence,” she said. “You start an organization to support someone, and by the end you don’t really support them at all.”

Kirsten Noyes contributed research.