(CNN) Nearly three weeks after sexual harassment allegations first emerged against Sen. Al Franken, a wave of Democratic senators — in coordination and following a flurry of text messages and phone calls — called for his resignation in rapid succession Wednesday morning .

Starting around 11:30 a.m. ET, the senators posted statements in a coordinated effort, one after the other, on social media, saying the Minnesota Democrat should step down.

Some comments were elaborate, lengthy and loaded with a moral message. Others, like that of Sen. Claire McCaskill of Missouri, were straight to the point.

"Al Franken should resign," she simply tweeted.

Within the next 90 minutes, 16 Democrats -- 10 of them women -- and one Republican senator -- Susan Collins of Maine -- had publicly urged their colleague to vacate his seat.

Capitol Hill had been on edge for weeks as more accusations were made public and as an ethics investigation was looming, yet no one had publicly called for Franken's resignation.

Meanwhile, giants in other industries like Hollywood and the news media were being fired or quickly taken down for similar allegations. In the US House of Representatives, Democratic leaders were calling for two of their own -- longtime Rep. John Conyers of Michigan and freshman Rep. Ruben Kihuen of Nevada -- to step down amid allegations of unwanted sexual advances.

In the Senate, however, it was quiet. Until Wednesday.

Women Democratic senators had been talking behind the scenes for at least the past week about how to deal with Franken, multiple aides told CNN. But those talks reached a tipping point Wednesday morning, they said, when Politico published a report at 9 a.m. ET of another woman alleging that Franken touched her inappropriately in 2006 , before he was elected to office.

The story prompted a flurry of calls and texts between Senate offices within minutes, and it was decided sometime between then and about 10:30 a.m. ET that the women senators would go public in a show of unity with their desire for Franken to step aside.

"Their patience had worn incredibly thin," said an aide to one of the women senators.

Soon after that, Franken was given a heads up about what was coming, according to an aide to one of the women senators.

They would time their statements so that the first one came from Sen. Kirsten Gillibrand of New York, who's been at the forefront of sexual harassment legislation in recent years. Her statement landed on Facebook at about 11:30 a.m. ET, roughly the same time she started an already-scheduled news conference on sexual harassment in the workplace. She was accompanied by others, like Republican Sen. Lindsey Graham of South Carolina and former Fox News host Gretchen Carlson, who famously filed a lawsuit against her news organization for sexual harassment that was settled for $20 million.

"While Senator Franken is entitled to have the Ethics Committee conclude its review, I believe it would be better for our country if he sent a clear message that any kind of mistreatment of women in our society isn't acceptable by stepping aside to let someone else serve," Gillibrand wrote in a 650-word statement.

Her statement came a day after Gillibrand, who's frequently cited as a potential candidate for president in 2020, struggled publicly to answer direct questions about whether Franken should resign. At an event hosted by Politico, she grew visibly and audibly angry, but would not directly answer the question. "I'm telling you, I'm so angry and frustrated and I'm not going to say that today," she said. "But it is something I am very troubled about."

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Wednesday morning, news organizations struggled to keep up with developments as the next resignation call rolled in, this time in a series of tweets from Sen. Mazie Hirono of Hawaii. "I've struggled with this decision because he's been a good Senator and I consider him a friend. But that cannot excuse his behavior and his mistreatment of women," she tweeted.

Seconds later, more women senators were taking part, sending a jolt through Washington one at a time.

Close to noon, their male Democratic colleagues started to weigh in, beginning with Sen. Bob Casey of Pennsylvania, saying on Twitter he agreed with his colleagues that Franken should step down.

While the behind-the-scenes discussions between the women were inevitably heading toward resignation calls, multiple aides said, it was the Politico report that set off the avalanche. Sen. Patty Murray, the highest-ranking woman Democrat in the Senate and No. 3 Democrat in the Senate, said the story showed Franken's behavior was a "persistent pattern" that needed to be addressed.

Like many others, Sen. Kamala Harris of California described it as a "difficult decision" but said "frankly the numerosity of the complaints I found to have weight."

Sen. Dick Durbin of Illinois, the No. 2 Democrat in the Senate, said he initially thought the accusations last month "might have been an isolated incident" but "it just seemed like the charges, credible charges, continued."

The other senator from Minnesota, Amy Klobuchar, was quieter than others, but her office put out a statement saying she had spoken to Franken Wednesday morning.

By the time this story published, the number of Democrats wanting Franken to resign had swelled to 28.

In the meantime, Franken's press office sent out an email to reporters.

"Wanted to let you know that Senator Franken will be making an announcement tomorrow," the email said. "More details to come."