Updated at 7:51 p.m. ET
Sen. Al Franken, D-Minn., plans to announce his resignation on Thursday, a Democratic official tells Minnesota Public Radio. The official spoke to Franken and key aides, MPR News reports.
Franken's office, however, says that "no final decision has been made."
If Franken resigns, Minnesota Gov. Mark Dayton, a Democrat, would appoint Franken's successor, who would serve until a special election is held in 2018. The winner of that special election would serve out the remainder of Franken's term until 2020, MPR also reported.
On Wednesday, more than half of the Democrats in the Senate, including party leadership called for Franken to step down amid allegations that he inappropriately touched several women.
"I consider Senator Franken a dear friend and greatly respect his accomplishments, but he has a higher obligation to his constituents and the Senate, and he should step down immediately," Sen. Chuck Schumer, D-N.Y., said in a statement.
Sen. Dick Durbin, D-Ill., the No. 2 Democrat in the Senate, tweeted that "Franken's behavior was wrong. He has admitted to what he did. He should resign from the Senate."
"I'm shocked and appalled by Senator Franken's behavior," Sen. Patty Murray, D-Wash., the Senate's No. 3 Democrat, tweeted, "It's clear to me that this has been a deeply harmful, persistent problem and a clear pattern over a long period of time. It's time for him to step aside."
Sens. Kirsten Gillibrand, D-N.Y.; Mazie Hirono, D-Hawaii; Kamala Harris, D-Calif.; Claire McCaskill, D-Mo.; Maggie Hassan, D-N.H.; Tammy Baldwin, D-Wis.; Debbie Stabenow, D-Mich.; Maria Cantwell, D-Wash.; Heidi Heitkamp, D-N.D.; Catherine Cortez Masto, D-Nev.; Sen. Tammy Duckworth, D-Ill.; Sen. Dianne Feinstein, D-Calif.; and Sen. Amy Klobuchar, D-Minn., also issued statements or postings on social media Wednesday calling on Franken to step down.
Gillibrand, in a Facebook post, said she has been "shocked and disappointed" to learn that a colleague whom she is "fond of personally has engaged in behavior towards women that is unacceptable."
In her statement, Hirono cited Time magazine's naming of the "#MeToo" movement as its Person of the Year, saying it recognized what "women have always known: There are men among us who use their positions of power and influence to manipulate, harass and assault women." Hirono said she struggled with her decision, calling Franken "a good Senator and a friend. "But," she said, "that cannot excuse his behavior and his treatment of women."
The 14 women were joined by 17 male Senate Democrats: Schumer, Durbin, and Sens. Bob Casey of Pennsylvania, Sherrod Brown of Ohio, Joe Donnelly of Indiana, Michael Bennet of Colorado, Patrick Leahy of Vermont, Ed Markey of Massachusetts, Jeff Merkley of Oregon, Tom Carper of Delaware, Martin Heinrich of New Mexico, Gary Peters of Michigan, Tom Udall of New Mexico, Sheldon Whitehouse of Rhode Island, Cory Booker of New Jersey, Jon Tester of Montana, and Ron Wyden of Oregon. In addition, Sens. Bernie Sanders of Vermont and Angus King of Maine — both independents who caucus with Senate Democrats — have called on Franken to step down. Tom Perez, chairman of the Democratic National Committee, also called on Franken to resign.
There is mounting frustration in the Senate Democratic Caucus about the allegations against Franken, according to three Senate Democratic aides who work for three of the senators calling for Franken to resign.
Franken's office said Wednesday that the senator will make an announcement Thursday but did not provide any more details. "Sexual harassment is unacceptable," Klobuchar, Franken's fellow Minnesota senator posted on Twitter. "This morning I spoke with Senator Franken and, as you know, he will be making an announcement about his future tomorrow morning. I am confident he will make the right decision."
Wednesday morning, Politico published a story about a new, anonymous accuser against Franken. The woman told Politico that Franken tried to forcibly kiss her in 2006. Franken denies that allegation.
And, Wednesday afternoon, The Atlantic published the account of writer Tina Dupuy who also alleged Franken had groped her in early 2009. It was not clear from the Atlantic report whether the publication had reached out to Franken for comment and, if so, how Franken had responded. In the story, Dupuy describes herself as a Democrat and takes on the decades-long history of her party and, more specifically left-leaning feminists coming to the defense of powerful Democratic men — including President Bill Clinton — who are accused of sexual misconduct.
"I have a radical idea: Maybe Democrats can replace politicians who harass and abuse women with anyone other than an abuser," DuPuy wrote. "Do we really believe our talent pool will dry up and our caucus will be nonexistent once we kick out all the creepers? I don't."
Several other women have said Franken engaged in sexual misconduct with them — including groping or kissing them or attempting to do so. Most but not all of the alleged incidents occurred before Franken was elected to the Senate. The Senate Ethics Committee has begun an inquiry into the allegations against Franken.
Speaking to Minnesota Public Radio in late November, Franken said at the time that he did not intend to resign. "I'm going to do my job, and I'm going to go forward," he said. "I'm going to take responsibility. I'm going to be held accountable, and I'm going to try to be productive in the way I speak about this."
"I have been reflecting on this," the two-term senator also told MPR early last week. "I want to be a better man."
The avalanche of calls Wednesday for Franken to step down came a day after Rep. John Conyers, D-Mich., announced his resignation after more than 50 years in the House of Representatives. The end of Conyers' half-century tenure in office was the result of days of pressure after multiple allegations of sexual harassment were leveled against him. Another House Democrat, Rep. Ruben Kihuen of Nevada, is also under pressure to resign after a former campaign staffer alleged he had sexually harassed her.
Sen. Michael Bennet, D-Colo.
"Sexual harassment and misconduct are never acceptable. I understand Senator Franken will make an announcement tomorrow morning, and I'm confident he'll do the right thing and step aside."
Sen. Cory Booker, D-N.J.
"Look there's a pattern here and I thought there was a process that could possibly deal with this pattern. I think today's revelations just further add to a fact pattern here that's unacceptable. I think it's time that he steps down and this is an opportunity for him to speak."
Sen. Sherrod Brown, D-Ohio
"I have listened to my female colleagues, to women I work with and women in my life. And I agree the time has come for Senator Franken to step aside."
Sen. Maria Cantwell, D-Wash.
"Senator Franken's actions are disturbing, egregious, and demonstrate a pattern of serious misconduct and abuse. It is time for Senator Franken to resign from office."
Sen. Tom Carper, D-Del.
"Al Franken has been a friend to many in the Senate — Republicans, Democrats and Independents alike — but these allegations are deeply troubling, especially as the number has grown. I believe it's time for him to resign."
Sen. Bob Casey, D-Pa.
"I agree with my colleagues who have stepped forward and called on Senator Franken to resign. We can't just believe women when it's convenient."
Sen. Catherine Cortez Masto, D-Nev.
"Sexual harassment in any context is unacceptable. I'm disappointed & disgusted with the allegations concerning @SenFranken, and he should be held accountable."
Sen. Joe Donnelly, D-Ind.
"Senator Franken's conduct and behavior are unacceptable and he should resign."
Sen. Tammy Duckworth, D-Ill.
"I am deeply disappointed by Senator Franken's behavior. He must step aside."
Sen. Dick Durbin, D-Ill., No. 2 Democrat in the Senate
"Senator Franken's behavior was wrong. He has admitted to what he did. He should resign from the Senate."
Sen. Dianne Feinstein, D-Calif.
"It's clear the American people don't look lightly on these kinds of actions, no matter who they're committed by, and the number of complaints against Senator Franken is a concern. I think resignation is the right thing for him to do."
Sen. Kirsten Gillibrand, D-N.Y.
"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."
Sen. Kamala Harris, D-Calif.
"Sexual harassment and misconduct should not be allowed by anyone and should not occur anywhere. I believe the best thing for Senator Franken to do is step down."
Sen. Maggie Hassan, D-N.H.
"It is clear that Al Franken has engaged in a pattern of egregious and unacceptable behavior toward women. He should resign."
Sen. Martin Heinrich, D-N.M.
"Senator Franken needs to step down and we all need to do more to make clear that sexual harassment and assault are unacceptable."
Sen. Heidi Heitkamp, D-N.D.
"We must commit to zero tolerance — which is where I believe we as a country and Congress should be — and that means Senator Franken should step down."
Sen. Mazie Hirono, D-Hawaii
"Today, I am calling on my colleague Al Franken to step aside. 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."
Sen. Angus King, I-Maine, caucuses with Senate Democrats
"A big part of the national conversation we're having on sexual assault involves listening carefully and with respect to women. I urge Sen. Franken to do just that: Listen to the Senate's female leaders and evaluate if he can continue to be an effective Senator for people of Minnesota, given the growing number of allegations against him. For me, I think it's time for my friend to resign."
Sen. Amy Klobuchar, D-Minn.
"Sexual harassment is unacceptable. This morning I spoke with Senator Franken and, as you know, he will be making an announcement about his future tomorrow morning. I am confident he will make the right decision."
Sen. Patrick Leahy, D-Vt.
"Senator Franken's situation has become untenable. I am concerned that even a prompt Ethics Committee investigation and recommendations will not come soon enough. He has to step aside."
Sen. Ed Markey, D-Mass.
"I join my colleagues in calling for Senator Franken to step aside and resign. Sexual harassment is unacceptable, completely inappropriate and cannot be tolerated."
Sen. Claire McCaskill, D-Mo.
"Al Franken should resign."
Sen. Jeff Merkley, D-Ore.
"Senator Franken has said he will make an announcement tomorrow, and I hope that he will do the right thing. It is in the best interest of our country for him to step aside."
Sen. Patty Murray, D-Wash., the No 3. Democrat in the Senate
"I'm shocked and appalled by Senator Franken's behavior. It's clear to me that this has been a deeply harmful, persistent problem and a clear pattern over a long period of time. It's time for him to step aside."
Tom Perez, chairman of the Democratic National Committee
Sen. Al Franken should step down. Everyone must share the responsibility of building a culture of trust and respect for women in everyday industry and workplace, and that includes our party."
Sen. Gary Peters, D-Mich.
"I think the time has come for Senator Franken to step down."
Sen. Bernie Sanders, I-Vt., caucuses with Senate Democrats
"Sen. Franken has said that he will be making an announcement about his political future tomorrow. The right thing is for him to resign."
Sen. Chuck Schumer, D-N.Y., Senate Minority Leader
"Senator Franken should resign. I consider Senator Franken a dear friend and greatly respect his accomplishments, but he has a higher obligation to his constituents and the Senate, and he should step down immediately."
Sen. Debbie Stabenow, D-Mich.
"Sexual harassment is unacceptable. I believe Senator Franken should do the right thing and resign."
Sen. Jon Tester, D-Mont.
"Elected officials must be held to a high standard, Al Franken is no exception. It's time for him to step down."
Sen. Tom Udall, D-N.M.
"Senator Franken should send a strong message that sexual misconduct is unacceptable in any setting and step down."
Sen. Sheldon Whitehouse, D-R.I.
"Given what we have learned in recent weeks, I expect Senator Franken to step aside."
Sen. Ron Wyden, D-Ore.
"I expect that Senator Franken will announce his resignation tomorrow. It is the right thing to do given this series of serious allegations."
NPR congressional correspondent Susan Davis and NPR producer Brakkton Booker contributed to this report.