Planned Parenthood’s political wing invested $30 million to encourage voters to turn out in last year’s elections alone. That effort fell short, but it will introduce a blitz ahead of the Senate vote, using a surge of donations since Mr. Trump’s election to press supporters to call their senators. Protests are also planned in Washington.

“Sometimes you have this phenomenon where everyone freaks out in the moment, signs a petition and then goes back to their everyday life,” says Ilyse Hogue, president of Naral Pro-Choice America. “But that’s not what we’re seeing. We’re seeing really high levels of retention and engagement.”

Anti-abortion groups are also gearing up for the Senate vote. Ms. Collins plans to amend the health care bill to restore Planned Parenthood funding, giving Democrats a conundrum: They may strongly favor supporting Planned Parenthood, but Democratic aides say senators must decide whether the bill has a better chance of passing with or without the defunding provision. If they think the Collins amendment would help final passage, they are likely to vote against it, ensuring its defeat.

That would be fine for the anti-abortion forces.

“As the Republicans start negotiating with the Democrats or with more moderate members, this is one of the hot-button topics that comes up that they try to negotiate away,” Mr. Seago said. “We will keep pressure on the Texans in D.C. to ensure this isn’t a bargaining chip to make sure this bill goes across the finishing line.”

Kristan Hawkins, the president of Students for Life of America, an anti-abortion group, toured 80 college campuses this spring, preparing for this moment.

“We can’t afford to wait around. We can’t afford to rest on our laurels,” Ms. Hawkins said.

The proposed legislation, which Planned Parenthood labels “the worst bill for women’s health in a generation,” would strip the organization of federal funding for one year and bar any federal tax credits from being used to help buy private health plans that cover abortions.