Senator Kirsten Gillibrand has spent years fighting the problems of sexual assault and harassment in the military and on college campuses.

Now, the junior senator from New York is calling for a reckoning on her own campus, Capitol Hill. She has called out the president of the United States and long-time Democratic allies like former President Bill Clinton and Senator Al Franken.

That candor and her willingness to be out front, often alone, has made her both a lightning rod and one of the most prominent political faces of the #MeToo movement.

In December, she was the first to publicly call for Senator Al Franken to resign.

Sen. Kirsten Gillibrand CBS News

Sen. Kirsten Gillibrand: I have a 14-year old son. And-- I cannot have a conversation that says, "Well, it's okay to grab somebody here but not there." It's not okay at all. You don't grab women. You don't push yourself on them.

Senator Kirsten Gillibrand told us Minnesota Democrat Al Franken is a friend but after eight women accused him of sexual misconduct, she was the first to publicly say he needed to go.

Sen. Kirsten Gillibrand: We just heard allegation after allegation. They were credible allegations. I believed the women.

Franken hoped a congressional investigation would clear him.

Al Franken: It's going to take a long time for me to regain peoples' trust.

Sen. Kirsten Gillibrand: "Enough is enough."

But Gillibrand was unwilling to wait.

Sharyn Alfonsi: But you're a lawyer. You believe in due process. Why not allow--

Sen. Kirsten Gillibrand: He's entitled to as much due process as he wants. He doesn't ever have to resign. That's his choice.

Sharyn Alfonsi: But it-- it feels so--

Sen. Kirsten Gillibrand: And my choice is to speak out.

Sharyn Alfonsi: But it feels like, to be accused right now, is to be convicted.

Sen. Kirsten Gillibrand: That's not right. That's not true. One of my colleagues recently was accused of something. Not only did he call the police—but there'll be an investigation.

Sharyn Alfonsi: But-- what is the harm in-- in waiting and letting all of the facts come out and-- to-- going into an investigation? Where is the harm in that?

Sen. Kirsten Gillibrand: Where's my moral compass if I can't speak out just because I like someone? Just because they're my friend? It's okay to be a harasser as long as you're my friend? That is not okay.

Correspondent Sharyn Alfonsi and Sen. Kirsten Gillibrand CBS News

Furious Democrats called her a traitor. But on this subject, Gillibrand is unapologetic. She took on Democratic icon Bill Clinton. In her Washington office she told us why she now believes Clinton should have resigned amid the Monica Lewinsky scandal.

Sharyn Alfonsi: Your critics will say, "What's going on here? You know, she took Senator Clinton's seat. She campaigned with Bill Clinton and Hillary Clinton. And now all of a sudden she's saying he should have resigned." Why didn't this happen-- or why did--

Sen. Kirsten Gillibrand: 'Cause I wasn't--

Sharyn Alfonsi: --why now?

Sen. Kirsten Gillibrand: --I wasn't focused on it in the way I am today. I didn't have that lens. I--

Sharyn Alfonsi: What do you mean had that lens?

Sen. Kirsten Gillibrand: All of us. I-- I think I'm not alone here. Like, how many of us were having this conversation even a year ago?

Sharyn Alfonsi: We're learning.

Sen. Kirsten Gillibrand: I think we're all learning.

Sharyn Alfonsi: Have you spoken to the Clintons since you said this?

Sen. Kirsten Gillibrand: Well, I don't wanna talk about that, but-- I can tell you one thing. I can tell you that-- Hillary Clinton is still my greatest role model in politics.

Gillibrand also called out President Donald Trump for a long history of alleged sexual misconduct.

Sharyn Alfonsi: The accusations aren't new against him. The voters saw the Access Hollywood tape and voted for him anyway. So why now?

Sen. Kirsten Gillibrand: Once President Trump was elected I think something changed, and I think it changed for women.

Sharyn Alfonsi: Do you think he'll be held accountable--

Sen. Kirsten Gillibrand: Well, I--

Sharyn Alfonsi: --in any way--

Sen. Kirsten Gillibrand: --I think he should resign, and if he's unwilling to do that, which is what I assume, then Congress should hold him accountable. We are obligated to have hearings.

President Trump responded to Gillibrand's criticism by trolling her on Twitter. He called her a lightweight.

Sharyn Alfonsi: He wrote, "She was-- she would be begging for contributions and would," quote, "do anything for them." How did you interpret that?

Sen. Kirsten Gillibrand: As being a sexist smear. there's ways to undermine women and belittle women, and that's one of them. And to minimize them and to silence them.

Gillibrand tweeted back, "You cannot silence me...about the unfitness and shame you have brought to the oval office". In this Twitter fight, Gillibrand drew six times more retweets than the president.

Sharyn Alfonsi: you've said-- you think Congress is an old boys club. Do you still think that?

Sen. Kirsten Gillibrand: Oh, it's definitely an old boys club. We only have 21 women in the U.S Senate. We need 51 and that will be representative of the nation.

Sharyn Alfonsi: Why do you think more women haven't run in the past?

Sen. Kirsten Gillibrand: I think fear, I think they thought--

Sharyn Alfonsi: Fear.

Sen. Kirsten Gillibrand: --someone else would take care of it. I think it's hard to run for office. It's-- it, you know, a lot of women don't like the negative campaigning, they don't like the aggressiveness of it.

Sen. Kirsten Gillibrand CBS News

Gillibrand entered the political fray in 2006 when she ran for Congress in a reliably Republican district known for having more cows than Democrats.

CAMPAIGN JINGLE: "If you've had enough of hypocrisy then vote for Gillibrand."

Surprisingly, she won. In early 2009, another surprise.

Then-New York Governor David Paterson named little know Gillibrand to finish Hillary Clinton's Senate term when she became Secretary of State.

Sharyn Alfonsi: This is the seat that everybody wanted. Andrew Cuomo apparently wanted it. Caroline Kennedy wanted it. And you got it.

Sen. Kirsten Gillibrand: Yeah.

Sharyn Alfonsi: How?

Sen. Kirsten Gillibrand: Was pretty shocking.I don't know

Sharyn Alfonsi: Did you ever ask him, "Why'd you choose me?"

Sen. Kirsten Gillibrand: No. I just said, "Thank you."

She was nicknamed 'the accidental senator,' but quickly earned a reputation as a hard worker. Some colleagues, unnerved by her peppy determination, called her something else, the name of the overachieving high school student in the movie "Election."

Sharyn Alfonsi: What did you think of being called Tracy Flick?

Sen. Kirsten Gillibrand: I really like Reese Witherspoon. So I didn't really care. I didn't care. I mean I knew what they were trying to say.

Sharyn Alfonsi: Yeah.

Sen. Kirsten Gillibrand: They were trying to be mean.

Sharyn Alfonsi: But was that a sexist comment, saying that you were overly ambitious?

Sen. Kirsten Gillibrand:Yes, of course. Of course it was.

Gillibrand says she is ambitious and always has been. Married to British-born business consultant Jonathan Gillibrand.

The couple has two sons. She is one of only two female senators with young children.

She was raised Catholic in Albany, New York.

Part of a deeply connected political family, for more than 40 years, her grandmother, Polly Noonan was a back-room power broker at the State House.

Sharyn Alfonsi: It's called Noonan Lane?

Sen. Kirsten Gillibrand: Noonan Lane. My grandmother bought all this property a long, long time ago. So this is the pond where I learned how to canoe in the summer. I also learned how to skate in the winter.

Her father was lawyer and powerful lobbyist. Her mother, also named polly says he was the one who nicknamed gillibrand "foghorn" as a child.

Sharyn Alfonsi: She was loud.

Polly Noonan: She was so loud that at one point I said to my husband, I said, "God, she's got to have a hearing problem. I think we'd better take her to the doctor for special testing." So we did. We had her tested and the doctor said, "Her hearing is fine."

Gillibrand's mother was a trailblazer too. A lawyer, with a black belt in karate.

She was also as a dead-eye hunter who proudly put a turkey on the Thanksgiving table year after year.

As a congresswoman, Gillibrand used that family tradition of hunting to appeal to conservative voters in upstate New York, she boasted an "A" rating from the NRA. Though Gillibrand still supports the second amendment, her stance has changed.

Sharyn Alfonsi: A few years ago, you said, "It has nothing to do with hunting. It has nothing to do with the Second Amendment." So why the 180?

Sen. Kirsten Gillibrand: After I got appointed, I went down to Brooklyn to meet with families who had suffered from gun violence in their communities. And you immediately experience the feeling that I couldn't have been more wrong. – you know I only had the lens of upstate New York.

Sharyn Alfonsi: But you had-- lived in New York City--

Sen. Kirsten Gillibrand: I know.

Sharyn Alfonsi: --for a decade.

Sen. Kirsten Gillibrand: And that's why I was embarrassed.

Sharyn Alfonsi: You traveled abroad.

Sen. Kirsten Gillibrand: I was wrong. What it's about is the power of the NRA and the greed of that industry. Let's be clear. It is not about hunters' rights, it's about money.

Sharyn Alfonsi: Your critics will say it's political opportunism.

Sen. Kirsten Gillibrand: As is their right. They can say what they like.

But it wasn't just her position on gun control that switched—as a congresswoman, her stance on immigration was closer to Donald Trump's than today's Senator Kirsten Gillibrand.

Sharyn Alfonsi: So can you understand President Trump's position on immigration, since you were there?

Sen. Kirsten Gillibrand: No. I think his positions are racist.

Sharyn Alfonsi: You were against amnesty, against sanctuary cities. You supported accelerated deportations. You become senator…Why the flip?

Sen. Kirsten Gillibrand: I came from a district that was 98% white. We have immigrants, but not a lot of immigrants. And I hadn't really spent the time to hear those kind of stories about what's it like to worry that your dad could be taken away at any moment, what it's like--

Sharyn Alfonsi: But you're reading the paper--

Sen. Kirsten Gillibrand: Yeah. And I just didn't take the time to understand why these issues mattered because it wasn't right in front of me. And that was my fault. It was something that I'm embarrassed about and I'm ashamed of.

Sharyn Alfonsi: So it is not very often that you hear a politician say, "I was wrong. I'm ashamed. I didn't know."

Sen. Kirsten Gillibrand: I just think as I've gotten older I've learned more about life and sometimes you're wrong. And you've gotta fix it. And if you're wrong, just admit it and move on.

With nine years in the Senate, the 51-year old Gillibrand has emerged as the political face of the #MeToo movement—prompting talk about her taking on President Trump in 2020. It is an ambition Gillibrand denies and she insists leading the fight against sexual assault has always been at the top of her political agenda.

Sen. Kirsten Gillibrand: Sexual assault is also reported to be the leading cause of post-traumatic stress disorder among women veterans.

Sen. Kirsten Gillibrand: I've been working for five years on trying to end sexual violence in the military, I've been working on trying to clean up sexual assault on college campuses because too many universities shove this stuff under the rug. And I now am trying to clean up Congress.

Gillibrand and other senators—including Republican Ted Cruz are pressuring Congress to change the way it deals with its own harassment complaints.

Sen. Kirsten Gillibrand: So today, if you are harassed in your office as a staffer here in Congress, You have to literally wait one month to have mandatory counseling, followed by one month--

Sharyn Alfonsi: Mandatory counseling for you?

Sen. Kirsten Gillibrand: For you--

Sharyn Alfonsi: For the accuser?

Sen. Kirsten Gillibrand: you the accuser. And then followed by one month of mandatory mediation with your harasser, followed by one month of cooling off. And then you're allowed to file your complaint. That is the status of the law today.

Sharyn Alfonsi: So three months?

Sen. Kirsten Gillibrand: Three months to wait.

Sharyn Alfonsi: So what do you think the intention of all that is?

Sen. Kirsten Gillibrand: To protect predators. To protect members of Congress.

As it is, members of Congress are allowed to settle harassment complaints with taxpayer money and keep it all confidential.

Sen. Kirsten Gillibrand: There are no doubt many, many more who want to speak out.

Gillibrand's call for transparency threatens to expose some of Capitol Hill's darkest secrets. She is unwavering in her crusade telling us on a trip to New York City that she is guided by her faith.

Sen. Kirsten Gillibrand: It really helps you remember that, you know, we are here to help people. We are here to put others first, to live a day in their shoes, to understand what their life is like and try to make it better.

It was Martin Luther King's birthday and Gillibrand confessed to a childhood dream of her own.

Sen. Kirsten Gillibrand: I wanted to be a preacher.

Sharyn Alfonsi: You did?

Sen. Kirsten Gillibrand: Yeah, that was one of the things I would've loved to have done. I was conflicted though, because I'm a Catholic, and they don't like—Catholics don't let women speak in the church.

Then, at a gathering in Harlem that afternoon, she quoted scripture like a revival tent evangelist--

Sen. Kirsten Gillibrand: "When the day of evil comes, you may stand your ground and after you have done everything, you stand!"

For Gillibrand, that's often meant standing alone—

Al Sharpton: "Reverend Kirsten Gillibrand."

Now surrounded by an amen chorus—

Gillibrand: "This is your moment!"

She's more determined than ever to be heard.

Produced by Howard L. Rosenberg and Julie Holstein.