Planned Parenthood is rallying supporters in anticipation of attempts by opponents in Congress to strip its federal funding.

A Republican majority in both houses of Congress and a Donald Trump administration are causing concerns that an effort to repeal the Affordable Care Act will include a renewed attack on Planned Parenthood.

Organizers are concerned that opponents will move swiftly to defund Planned Parenthood by preventing it from receiving reimbursement from Medicaid and other programs for health services such as cancer screening, birth control, sex education and STD testing. During the presidential campaign, Trump made statements in support of Planned Parenthood, but also said he would defund the organization. Vice President-elect Mike Pence is a staunch opponent of abortion and has long advocated for blocking federal funding to Planned Parenthood.

Although future action is unclear, reproductive rights advocates are preparing for the worst-case scenario of a combined action by a hostile Congress and Trump administration, said Nicole Clegg, vice president of public policy for Planned Parenthood Northern New England.

“This is unprecedented. We are facing something we have never seen before,” Clegg told volunteers at a training session Wednesday in Portland. “They have never done this with any other health care provider. It is unacceptable.”

The organization, which has four offices in southern Maine, relies on federal funds for about 40 percent of its budget, Clegg said. Nationally, the group receives about $450 million in federal money a year and provides care to 2.5 million people.

Although Planned Parenthood is an abortion provider, that only amounts to 3 percent of the services it offers. It focuses on providing reproductive and women’s health services, often to low-income people. Half of the 10,000 patients seen by the organization in Maine last year lived at 150 percent of the federal poverty line, and it provided $3.5 million worth of free or discounted health care, Clegg said. Planned Parenthood cannot receive federal reimbursement for abortion services except in the case of rape, incest or danger to the life of the mother.

The national Planned Parenthood organization and local offices are preparing to fight any defunding efforts. In the days after the election, Planned Parenthood was inundated with volunteers and donations. The national group received 315,000 individual donations, including 82,000 made in Pence’s name, Clegg said.

An action forum last month at Planned Parenthood’s Portland office attracted 110 supporters, more than double the number expected. At least 50 more attended another forum Wednesday. When Clegg asked the mostly female crowd how many had used the organization’s services, more than half raised their hands.

Among them was Ellen White, 28, a patient who recently signed up to volunteer. White first visited Planned Parenthood three years ago after she developed an extremely painful vaginal infection she couldn’t afford to treat at a doctor’s office or emergency room.

“I was just resigned, that was going to be my experience and there was nothing I could do about it,” White said, holding back tears. A friend referred her to the Planned Parenthood office and she has been coming regularly for services ever since, White said. The threat faced by the organization now is heartbreaking and despicable, she said.

“I see people in power with knowledge of what an organization like this really provides, twisting and distorting that information to rally people against a group that does so much good,” White said. Last year, congressional Republicans tried to prevent Planned Parenthood from receiving money as part of a federal funding bill. President Obama vetoed the bill in January,

Opponents have long tried to defund Planned Parenthood. The issue was inflamed by a secretly recorded video released by anti-abortion activists last summer allegedly showing a Planned Parenthood doctor discussing the disposal of aborted fetuses. Planned Parenthood has denounced the video as misleading and highly edited, and investigations have not found any wrongdoing.

A least 10 states have pushed measures to prevent Planned Parenthood from receiving Medicaid funds. On Tuesday, Texas moved ahead with blocking Medicaid funds beginning in January, despite a warning from the Obama administration that such a move could violate federal law.

Losing funding may be the first issue the organization faces, but Clegg said it is gearing up for a years-long fight against rollbacks to reproductive rights. Potential rollbacks include a ban on abortion after 20 weeks of pregnancy, and measures that say “personhood” begins at the moment of fertilization. There also is likely to be a conservative majority on the U.S. Supreme Court.

Although the pressure is intense, it is coming from a vocal and committed minority, Clegg said. According to Planned Parenthood, one in five women go to Planned Parenthood in their lifetime and seven in 10 Americans support the organization. A September survey by Politico and Harvard University found that almost 50 percent of Trump voters said the federal government should continue funding the organization.

“There was no conversation about Planned Parenthood or defunding us being a priority or a deciding factor for why people would vote for Donald Trump,” Clegg said. “There is no evidence that this is what people want, but here we are seeing it as a first act of Congress and a Trump administration.”