The annual March for Life antiabortion rally gathers at the Washington Monument on Jan. 22, 2016. Despite a looming snowstorm, marchers walked up Constitution Avenue toward a rally at the Supreme Court. (Evelyn Hockstein/For The Washington Post)

After 43 years of doggedly demonstrating against abortion at the annual March for Life each January, thousands of abortion opponents will gather Friday on the Mall with great reason for optimism. Just days into his presidency, Donald Trump has made abortion one of his first priorities in office.

With a likely eye toward rewarding voters who supported him based heavily on expectations that he would act on abortion, Trump has already revived an old policy banning U.S. funding for groups abroad that pay for abortions or provide information about abortion. On Tuesday, he signaled his intentions to nominate an antiabortion justice to the Supreme Court next week, and he has vowed more action to follow.

Kellyanne Conway, Trump’s senior counselor, will speak at the march, the highest-ranking White House official to ever attend the event, according to march organizers. Trump and Vice President Pence have also been invited.

“It’s going to be extremely joyful,” Kristan Hawkins, president of Students for Life, said of this year’s march. “People know action is coming. . . . [Trump] made his pro-life promises, and the pro-life movement is excited about those promises.”

The first march was held one year after the Supreme Court’s Roe v. Wade decision in 1973 that recognized a right to abortion nationwide. Subsequent marches have been held on or near the Jan. 22 anniversary every year since.

The past eight years’ marches have been grimmer affairs, with tens of thousands of antiabortion activists gathering to show their solidarity with one another and restate their opposition, but with little chance of having their hopes fulfilled on the federal level.

This year, change seems not only possible but imminent.

“It’s hard to describe the mood,” said Jeanne Mancini, president of the March for Life.

Mancini brightly rattled off her four demands for Trump and the new Republican Congress: Appoint an antiabortion justice to the Supreme Court. Make the Hyde Amendment, which bans federal funding for many abortions in the United States, into a permanent law rather than the one-year provision that has been extended each year from 1976 to the present. Pass a law banning abortion nationwide after 20 weeks of pregnancy. And stop all federal funding for Planned Parenthood unless the organization were to somehow stop performing abortions.

And Mancini wants to see it all accomplished immediately. To keep the support of abortion opponents, she said Trump must accomplish “those four things. All of them by this time next year.”

March participants’ antiabortion stance is counter to the position held by most Americans. Nationwide, 57 percent say abortion should be legal in all or most cases, the highest percentage since 1996, according to a 2016 Pew Research Center poll. Thirty-nine percent say it should be illegal in all or most cases, according to the poll. Eighty percent of Americans who do not affiliate with a faith group — a rapidly growing portion of the population — say abortion should be legal, according to the Pew poll.

Mancini and many others involved in the march noted that many in the movement had serious reservations about Trump as a candidate. “Some of the comments about women — it gave us all pause. A lot of pause,” she said. Still, Trump — a supporter of abortion rights before he ran for president — won most of their votes by vowing to appoint antiabortion judges, among other promises.

In addition to Conway, three Republican members of Congress — Sen. Joni Ernst (Iowa), Rep. Mia Love (Utah) and Rep. Christopher H. Smith (N.J.) — also are to speak before the group at the rally before participants march from the Mall to the Supreme Court, their annual route. Along with Catholic and evangelical leaders, the two guests bringing star power to the march are Baltimore Ravens player Benjamin Watson and Mexican telenovela actress Karyme Lozano.

Comparisons with last weekend’s Women’s March on Washington — at which celebrities including Madonna, Janelle Monáe and Scarlett Johansson appeared on stage — are inevitable. When that march started to come together, many who said they wanted to attend were also affiliated with the antiabortion movement — which has in recent years tried to emphasize its broader appeal, insisting that it attracts nonreligious people, enjoys popularity among youth and is rooted in concern for the well-being of women.

But then the Women’s March listed abortion access as one of its official demands and dropped an antiabortion group from the list of official partners. Many women who opposed abortion changed their minds about going, and others who appeared with their antiabortion signs were met with loud shouts of “my body, my choice” by other marchers.

The rejection of these women during the huge demonstration has only spurred their determination to show their presence on the Mall on Friday.

“It seems to me that there’s a lot of new energy, especially after the Women’s March,” said Charles Camosy, a Fordham University professor on the board of Democrats for Life of America. “People who identify as ‘pro-life feminists’ have to convince people that it’s a thing. . . . There’s a new kind of energy going into this march.”

The March for Life is unlikely to draw as large a crowd as the Women’s March or Trump’s inauguration, but organizers said they hope for hundreds of thousands of participants. In recent years, turnout has generally hovered in the tens of thousands. EventsDC said that 92 buses have obtained permits to park at RFK Stadium on Friday, compared with 450 buses that requested permits for Inauguration Day and 1,200 buses for the Women’s March. Metro, anticipating a large crowd, will run extra trains on Friday, just as it did for the Women’s March this past Saturday.

Toni Papp will have the Women’s March in mind when she attends the March for Life, her 17th. She was impressed by the gathering’s size and passion, but not by its stance on abortion.

“It did not respect what I think empowerment of women is. It did not respect all human beings, because it supported killing human baby girls,” said Papp, who runs the youth ministry at Holy Family Catholic Church in Prince William County, Va.

Aimee Murphy, the founder of Life Matters Journal, joined the Women’s March despite the abortion rights plank. Murphy, 28, said she received a range of reactions, from people who said “thank you for being here” to others who yelled at her.

At Friday’s march, Murphy said she will call participants to “a more consistent approach to the right to life” and ask them to “appreciate the feminist part of pro-life.”

“We can’t just love the baby,” Murphy said. “We have to stand for the rights of the woman.”

For decades, the march was run largely by a Virginia woman named Nellie Gray, who died in 2012. Always strongly Catholic-based and attended by many Catholic school groups, the march draws attendees from across the country and has in recent years attracted more evangelicals.

Nearly 70 percent of white evangelicals think that abortion should be illegal in all or most cases, while 54 percent of Catholics say that abortion should be legal, according to the Pew Research Center.

Several attendees said that they worry that the enthusiasm for Trump at this year’s march will damage the antiabortion movement’s attempts at wooing younger people and non-religious people, who were less likely to have voted for the president.

“With Donald Trump as the standard-bearer . . . it plays into all sorts of stereotypes: That we’re old white men who want to control women’s bodies,” said Camosy, the Democrats for Life board member.

But for many who flock to the march, Trump’s inauguration represented a moment of hope, sparking an optimism that they will carry to the Mall on Friday.

While Mary Comer prays for an end to abortion at her Catholic church in Clarksville, Md., her husband Bob Comer — a father of two, a grandfather of seven and an atheist — will be out marching.

“When I look at pictures of unborn children in their mother’s womb, it’s a person, and there’s no denying it’s a person from conception,” said Bob Comer, 71.

Comer has marched for the past several years, and he’s looking forward to this year’s spirit of “joy and fellowship.”

“Joy coming from knowing that we are heard, that we are listened to, and that hopefully something will be done, some concrete measures will be taken. And fellowship because we’re with like-minded people,” he said.

Perry Stein contributed to this report.