Also at stake is the Affordable Care Act, the repeal of which could leave millions of women without health insurance and unable to receive reproductive care. The requirement that insurers cover contraceptives without a co-pay is vulnerable even if the law stands; because it is a regulation, it could be reversed by a new administration.

Yet under a president committed to reproductive rights several restrictions currently in place could be loosened or removed. Hillary Clinton took an important stand when she called for a repeal of the Hyde Amendment, which bars federal programs like Medicaid from paying for most abortions and has long been treated as politically untouchable. Senator Bernie Sanders followed suit, saying, “Women must have full control over their reproductive health in order to have full control over their lives.”

While a full repeal of the Hyde Amendment would be unlikely without a major change in the makeup of Congress, other, similar restrictions are less entrenched — a ban on the use of local government funds to pay for abortions in Washington, D.C., was repealed in 2009, though it was reinstated in 2011.

Mr. Sanders and Mrs. Clinton have also addressed the Helms Amendment, which bans the use of foreign aid to pay for abortion “as a method of family planning.” Since 1973, presidents have interpreted this ban as absolute, but Mr. Sanders has promised to take executive action to allow exceptions in the cases of rape, incest or a risk to the life of the mother, and to work with Congress to repeal the amendment altogether. Mrs. Clinton has also said she would reinterpret the amendment, and a spokesman for her campaign says she would support a repeal.

The Republican candidates, meanwhile, are all anti-choice. Senator Marco Rubio, Senator Ted Cruz and Ben Carson oppose abortion even in cases of rape or incest. Mr. Trump and Gov. John Kasich would allow abortion in those extreme circumstances. Mr. Kasich has been a tireless opponent of abortion rights in Ohio. Last week, he signed a bill that will deprive Planned Parenthood of $1.3 million in state Health Department funds. Planned Parenthood had used these funds not for abortions, but for H.I.V. testing, domestic violence education and an infant mortality prevention program, among other services.