When Donald Trump ran for president in 2016, he promised to put the Supreme Court on a path to “automatically” overturn the decades-old precedent established in Roe v. Wade, which established a woman’s constitutional right to abortion.

After five years and three Supreme Court nominees, conservatives see a wave of pending abortion appeals as the best opportunity in a generation to put that commitment to the test. By announcing Monday that it will hear a challenge to Mississippi’s ban on most abortions after 15 weeks of pregnancy, the Supreme Court signaled its willingness to reconsider.

With six conservatives on the nine-member court for the first time in decades and uncertainty over a 2019 Supreme Court decision scrambling lower courts, anti-abortion lawmakers and advocates are leaning in to test the limits of the 1973 Roe v. Wade decision and a landmark 1992 case that currently controls when states may regulate the procedure.

The court’s decision to hear the Mississippi ban, with a decision expected early next year, could be the first of many such appeals.

According to the anti-abortion advocacy group Susan B. Anthony List, at least 23 abortion-related cases are pending in federal appeals courts. Meanwhile, conservative states are rapidly enacting new legislation. According to the Guttmacher Institute, a research group that supports abortion rights, state lawmakers have enacted 61 abortion restrictions so far this year, compared to 42 at the same point in 2011, the previous year with the highest number of such laws.

“What we’re seeing is huge numbers of abortion restrictions being passed at the state level,” said Julie Rikelman, litigation director at the Center for Reproductive Rights. “And it’s clear that it’s all part of a coordinated national strategy to either make abortion completely inaccessible or to push it out of reach through any means necessary.”

Two trends are fueling anti-abortion groups’ optimism: A more conservative Supreme Court, as well as a number of diverging opinions in federal appeals courts on how to interpret similar laws, have created “circuit splits” that only the Supreme Court can resolve. Appeals courts in Chicago and St. Louis, for example, have blocked abortion bans in cases where a fetus has Down syndrome. However, an appeals court in Ohio upheld a similar ban last month, allowing the law to remain in effect.

“Pro-life activists have new hope that the Supreme Court will address the abortion issue,” said Mallory Quigley, spokesperson for Susan B. Anthony List. “None of these splits guarantees a pro-life outcome from the court, although we are hopeful given the new makeup of the court post the Trump-Pence administration.”

After avoiding the abortion issue in a number of recent cases, the Supreme Court surprised some observers Monday by announcing it would hear an appeal from Mississippi, one of several states with laws prohibiting abortion before a fetus is viable outside the womb, the standard set by the Planned Parenthood v. Casey decision in 1992. Lower courts overturned Mississippi’s law, claiming it violated the precedent established in that landmark decision.

Many of the appeals pending in lower courts aren’t directly challenging Roe, but rather Casey, which held that states can regulate abortion as long as they don’t impose a “undue burden” on a woman’s right to terminate a pregnancy.

Some laws require a woman to wait 48 hours before having an abortion. Others prohibit the procedure if it is performed for a specific reason, such as a genetic abnormality. Some propose prohibiting the type of abortion procedure used. Abortion rights advocates claim that all of them are underhanded attempts to limit a woman’s ability to terminate a pregnancy.

According to some experts, the decision to hear the Mississippi case indicates that at least some conservatives want to reconsider the legal framework established by Roe and Casey. It only takes four justices to agree to hear a case, and it takes five to win it.