“The president is going to speak here today, the first time in history,” he said, smiling. “That really puts a lot of horsepower behind our movement.”

Mr. Hagemyer said Mr. Trump’s support makes him even more optimistic about the future. “I firmly believe that in my lifetime we will see Roe v. Wade overturned,” he said referring to the landmark 1973 Supreme Court ruling that extended federal protections to abortion. “The tide is turning. People are starting to realize abortion is not something we should be doing.”

But Alexis McGill Johnson, the acting president and chief executive of the Planned Parenthood Action Fund, pushed back on that idea in a statement after Mr. Trump’s appearance.

“While Trump stands with the small number of Americans who want politicians to interfere with their personal health decisions, we’ll be standing with the nearly 80 percent of Americans who support abortion access,” Ms. Johnson said. “We will never stop fighting for all of the people in this country who need access to sexual and reproductive health care, including abortion.”

Mr. Trump’s relationship with the anti-abortion movement has been a transactional one since he entered politics in the 2016 presidential campaign. He has focused his efforts in particular on white evangelicals and Catholics, a critical part of his base in that campaign who could be even more important this November.

In exchange for the appointment of anti-abortion judges, his unwavering support for Israel and his attempts to protect the rights of students to pray in schools, they have generally overlooked Mr. Trump’s own complicated past with the issue and his own history of three marriages and two divorces.