This week, Arizona Rep. Ruben Gallego announced he would challenge Sen. Kyrsten Sinema for her U.S. Senate seat.

Sinema, the erstwhile Democrat who recently switched her party allegiance to independent, had come under fire from her fellow Democrats for voting down the $15 minimum wage, protecting the carried-income tax loophole that gives tax breaks to hedge fund managers and private equity executives, and blocking voting rights legislation. Former canvassers have said they feel betrayed by the Senator they helped elect, and her critics in the Arizona Democratic Party have accused her of avoiding public events. Her popularity is underwater in her state, and she has the second-lowest approval rating in the Senate, according to Morning Consult.

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All that has left Sinema vulnerable to a 2024 challenge. Democratic Rep. Gallego, a Marine Corps Iraq combat veteran who is serving his fifth term in Congress, is the first serious candidate to put his hat in the ring.

TIME spoke to Gallego in a coffee shop in the bowels of Rockefeller Center on Jan. 24 about his platform, his dark times after returning from the war, and how he turned from supporting Sen. Sinema to challenging her for her seat.

The following interview has been lightly edited and condensed.

TIME: Why are you challenging Sen. Kyrsten Sinema for this seat?

Gallego: She’s just abandoned Arizona. We hardly see her anywhere, she doesn’t have an unscripted moment, we see her fighting for pharmaceutical companies, for hedge fund managers. She skipped votes to go do the Iron Man in New Zealand. Her priorities aren’t the priorities of Arizonans anymore. There’s an opportunity to change that, and I’m going to do that.

What would you say are your three most important issues?

Passing the Child Tax Credit. My mom did amazing work, raising four kids on her own on a secretary’s salary; we were on school free lunch program, but she prides herself on never being on welfare or food stamps. I slept in the living room because we couldn’t afford a bigger apartment. That woman had so much stress on her. She didn’t want to raise these kids on her own, she would have loved to have stayed married, except my father was an a–hole; it was an extremely dangerous situation for her to stay with him. He was abusive to me, he was abusive to my mother. Every night I’d hear her crying because she’s just trying to figure out how to make this work. There’s millions of Americans who deal with this every day.

And for six months, we had this beautiful period where Americans had a little stress relief. I heard from parents all over the country who said for those six months, I didn’t have to worry about how I’m going to pay for childcare this month. For those six months, I didn’t have to go to overtime, I actually got to stay home with my kid. It reduces child poverty by 60%. This is the kind of thing that could be revolutionary to this country, and we just kind of gave it up.

Second, we have to deal with climate change and drought in Arizona. Our future is entirely tied with how we’re going to manage this.

And lastly, immigration reform. We can’t ignore what is happening at the border, we clearly have a refugee and asylum crisis. We can fix it, but right now everyone’s solution is one-sided. We passed three bipartisan immigration reform bills out of the House and they got to the Senate, and even though we had control of the Senate, we didn’t really because of the filibuster.

Where are you on the filibuster?

I think at a minimum, we should be reforming the filibuster. It’s clearly been abused over the last couple years, and now it’s now used as a tool of obstruction instead of to create room for compromise.

You mentioned in your launch video that there were some dark moments after you got back from serving as a Marine in Iraq. Can you tell me about that?

The biggest problem is you don’t really know who you are when you get back from the war, because you were a totally different person when you went. I was a lot more anxious, I was quick to get angry. You have survivor’s guilt. There were a couple times when I should have died instead of my friends dying because we switched places. There were times where instead of dealing with it in a smart, sane way, I decided to drink instead of going to a therapist. I never got into a DUI or anything like that, but it’s also not a healthy way to deal with anything. And instead of healthy relationships I focused on a superficial idea of success. Focusing on getting a job, getting a better job, when I was really internally just breaking apart.

It took years for me to accept where I was in terms of that problem, and finally got help. I never felt the urge for suicide or anything of that nature, but it’s a weird situation where you don’t feel like yourself anymore. Whenever I feel a flare-up coming, I go back to a therapist. But it’s never going to ever go away, it’s part of my life. A lot of times people think veterans or people with PTSD can’t function, like we’re these ticking time bombs and you can’t trust them with anything. That’s one of the reasons why I’m really open about talking about it. But it’s something you have to actively work on.

What were the most difficult periods?

The breaking point was when my son was coming, because I was afraid I was going to be a bad father. Especially coming from my background where I didn’t have a good father, it was a scary moment. I knew I was going to be a bad father if I didn’t work on my PTSD.

But you don’t really have good years or bad years, you just have years. We’re 17, 18 years removed. Sh-t, my PTSD can vote!

You used to be a strong supporter of Senator Sinema’s, what do you anticipate her pushback will be?

Nobody trusts her. She has a lot of trust to repair with voters, and she’s not gonna take the necessary steps to do that: talking to people that you’ve pissed off the last four years, people you’ve ignored, people you don’t return phone calls from. A lot of us were with her from day one. I’ve been a big supporter of hers since even before she got to the Senate. There are thousands of people in Arizona that feel that way that are gonna have their say.

What was your breaking point? Take me through your period of disillusionment.

That sounds like a Gabriel García Márquez title right there. We always knew that Sinema was maybe more conservative than we would have liked, but we all felt that when push came to shove, she was going to be with us.

But post-January 6, after talking about being friends with John Lewis and John Lewis being her mentor, she uses the filibuster to stop the John Lewis Voting Rights Act.

And then it was other things that kept on moving in that direction, whether it was rejecting the $15 per hour minimum wage or negotiating for pharmaceutical companies to keep their pricing. Or lastly, when she went to the floor to fight for private equity managers and hedge fund managers, while the poor in Arizona are hoping to get a Child Tax Credit.

So how did you get from there to deciding to challenge her?

Knowing Kyrsten, and knowing Arizona, I also knew that nobody would take her on. In Arizona she has a reputation for being a very fierce fighter. We know she has a lot of support from the money groups. At the end of the day you can complain all you want, but she doesn’t change because of that; she doesn’t really care about the opinions of Arizonans, she doesn’t care about the opinions of anybody except for a few people. And so in order to make change, we have to get her out of the way.

Obviously there’s going to be a Republican challenger, and Arizona has a lot of independents. What is your strategy to make sure Democrats come out on top?

Our first place strategy is to solidify Democrats, and we think we have that in hand already. She is really, really unpopular and has been for quite a while. There’s also a large segment of Latinos that have not been engaged, that are going to be engaged, and are going to get excited about our race. People are talking about how proud they are that there is a Latino running, and they’re proud that it’s a Latino that comes from a working class background they actually understand. And I think energizing that young base is going to be extremely important. In Arizona, close to 5-6,000 Latinos turn 18 per month, and a lot of them are registering as independents. We’re going to be able to attract that vote. We’re going to energize the Native American vote; we’re probably one of the first campaigns to ever have a kickoff on Native American land. And we’re going to talk to people in red areas, we’re going to talk to anyone who wants to come to a town hall. We’re going to hit every county in Arizona.

What happens if potential Republican challengers like Kari Lake or Blake Masters create a narrative that you’re a far-left progressive?

So the same narrative they used on Sen. Mark Kelly and every Democrat last year? And in 2018, 2020, and 2022? They can say all they want about that, but the problem is that narrative doesn’t work.

Are you a progressive?

I definitely am in some areas and in some areas I’m in the mainstream norm. My voting record is almost the same as Mark Kelly’s.

What are the areas in which you’re a progressive?

Those labels keep moving around. I feel like now they’re just thrown at anything where people just want to say ‘that person’s bad.’

What is your message to independent Arizonans?

It is not independent nor is it moderate for you to be negotiating for pharmaceutical companies in Arizona. We’ve got Arizona seniors who are driving to Mexico to get cheaper drugs in Mexico than they could at Walgreens or CVS. That’s not moderate. It’s not moderate to be negotiating for private equity managers. Your Senator is supposed to be negotiating for you, not for people who have power. You may not agree with me 100% of the time as a citizen of Arizona, but I guarantee you’re always going to know where I stand.