Transcript for At Anti-Abortion Rally in D.C., Feelings of Triumph
Thank you for join is us. Anti-abortion rights activists swarmed the capital today, exuberant over the support they're receiving from the trump administration. Mike pence became the first sitting vice president in history to address the annual March for life rally,a signal to the crowd that for the first time in careers they may be in striking distance of major policy change. Here's ABC's Gloria Riviera. Reporter: Today in the nation's capital, a sea of signs and a chorus of chants. Pro-life! Reporter: With one singular goal in mind. Roe V. Wade has got to go! Reporter: The March for life happens every January. But this year many anti-abortion crusaders say they're seeing a window of opportunity in one of America's most controversial and enduring culture wars. This is what the anti-abortion rights movement looks like today at the dawn of the trump administration. We're outside the supreme court. The word I keep hearing from so many in the crowd is that for the first time in eight years, they feel hope. We've had people here from 10:00 this morning -- Reporter: Kristin hawkens, president of students for the life of America. We have a chance of abolishing abortion in our lifetime. We are the pro-life generation! Reporter: America's war over abortion rights has been raging over 40 years. Since the supreme court ruled it was legal in the case roe versus wade. While the most recent polls show 64% of Americans believe that abortion should be legal in all or most cases, a supreme court vacancy and republican-led congress could mean drastic changes to abortion rights in the coming years. That's why this administration will work with the congress to end taxpayer funding of abortion -- Reporter: The anti-abortion movement has a staunch ally in vice president Mike pence, the highest-ranking government official to ever attend the March for life. Life is winning in America. You are an activist in the anti-abortion rights movement. Correct. When you heard the vice president was going to speak, what did that feel like? It was amazing. It was amazing, so uplifting. Thinking, we might have a chance to actually, you know, do something here. Reporter: Pence is a long-time anti-abortion legislator. Government-wide prohibition on taxpayer funding for abortion has probably never been more important -- Reporter: As in congress he introduced a bill to end funding for planned parenthood, America's biggest reproductive health care provider. We will not rest until we restore a culture of life in America for ourselves and our posterity. This is a very difficult time to watch the care that so many people need in this country be threatened and to be at risk. So that's what planned parenthood is focused on every day, making sure people are getting care and that they can continue to get care. Reporter: One of his first orders of business, president trump reinstated a reagan-era policy prohibiting American foreign aid to health providers overseas who even discuss abortion as a family planning option. This morning, president trump tweeted his support for the March for life. He spoke about it to ABC's David Muir in response to a question about last Saturday's women's March. Let me just ask you while we're standing outside, could you hear the voices from the women's March here in Washington? We know there were more than 1 million people who turned out. You are their president now too. That's true. Could you hear them from the white house? No, I couldn't hear them. But the crowds were large, but you're going to have a large crowd on Friday too, which is mostly pro-life people. You're going to have a lot of people coming Friday. I will say this, and I didn't realize this, but I was told, you will have a very large crowd of people. I don't know, as large or larger. Some people say it's going to be larger, pro-life people. And they say the press doesn't cover them. Reporter: At the March for life two years ago, we met Kristen hawkens. There was a sense the odds were stacked against their movement. Are you going to give them more warning of an arrest? Way back. Why are you talking to the officers? What happened is the counter protesters decided to block the streets. The March for life has the permit. We need to show the world we're the life generation! We saw pro-choice advocates getting arrested, they got taken away. Yeah, it was great. I love our students to see that. Because they need to see that there are people who actually believe that killing a baby up to the moment of birth and sometimes after is still okay. Reporter: The mood today, less confrontation, more celebration. We met a mother returning to the March after two decades. You were here 20 years ago, why are you back now? We have a chance, with the new administration, with vice president pence, I'm so excited. For the first time in eight years we have a voice again. Reporter: At the March there were people as far as the eye can see. Hey, thank you! Walking with Kristen is like walking with a rock star. Reporter: Just blocks away, the president was busy making other news today. Meeting with British prime minister Theresa may, trying to find common ground on the phone with Mexican president Nieto, signing two executive orders, one designed to build up the military, the other to create a system of "Extreme vetting" for immigrants. A decisive start to acting on those campaign promises. But millions of women have been helped by planned parenthood. But we're not going to allow and we're not going to fund as long as you have the abortion going on at planned parenthood. Reporter: The marchers today hoping the president will make good on that one. The fight to defund planned parenthood is not new, but with Republicans in control of the house, the senate, and the white house, this battle is really at its peak right now. When we talk about the preventive health services that are actually threatened in a defunding scenario, breast cancer screenings, pap tests, birth control, STD testing and treatment, those are the kind of services that are threatened. Reporter: The other battleground, the supreme court, where many in the anti-abortion movement hope that roe versus wade could be overturned. What would you like to see on the supreme court? Just where life is valued. Reporter: President trump is expected to fill the vacant seat on the supreme court with a conservative justice. But it still wouldn't be enough to tip the scales. Most court watchers say five would likely vote to uphold, four would likely vote to strike down. The trump administration can restrict abortion rights, but roe V. Wade cannot be overturned any time soon. That's because it will take more than the one opening on the supreme court that Donald Trump curtly has. We believe that this has been the settled law of the land for 40 years. And absolutely roe V. Wade is something that any jurist should uphold and protect. We know when you make abortion illegal, you don't actually reduce abortion, you actually make it less safe. Reporter: Hawkens, however, believes overturning roe versus wade is. If you look at the reality, if you look at the supreme court appointments this president is going to be able to make, it's entirely possible. I think that's why you saw so many women come out and men come out, the so-called women's March last week, because they know just how close we are to abolishing abortion in this lifetime. Reporter: For "Nightline" I'm Gloria Riviera in Washington.
This transcript has been automatically generated and may not be 100% accurate.