Education Secretary Betsy DeVos compared the choice to have an abortion with the choice to own slaves, saying President Abraham Lincoln also had to contend with a misguided “pro-choice” argument.

DeVos drew barbs for the comparison, but the analogy between slavery and abortion is hardly novel. It is offensive to many who see slavery as America’s singular original sin, but it has been used for decades by abortion opponents seeking to bestow constitutional rights onto developing fetuses and to associate their movement with one that is far more unifying.

Politically, her comments could prove helpful. They are consistent with the views of her boss, President Trump, who has taken a hard-line stance against abortion rights and whose reelection depends on robust support from Christian conservatives. On Friday, he became the first president to speak at the annual antiabortion March for Life.

The education secretary’s remarks came Wednesday evening at an event for a Christian college held at the Museum of the Bible in the District. She touted the Trump administration’s work to advance antiabortion policies, including putting two conservative Supreme Court justices on the bench, and said she hopes to make abortion not just unconstitutional but “unthinkable.”

She then added that the abortion debate reminded her of President Lincoln, who led the fight to preserve the United States and stamp out slavery in the South.

“He too contended with the ‘pro-choice’ arguments of his day,” she said, according to a copy of her remarks provided by the Education Department. “They suggested that a state’s ‘choice’ to be slave or to be free had no moral question in it.”

She said Lincoln “reminded those pro-choicers” that most Americans viewed slavery as a “vast moral evil.”

“Lincoln was right about slavery ‘choice’ then, and he would be right about the life ‘choice’ today,” she said. “Freedom is not about doing what we want. Freedom is about having the right to do what we ought.”

In DeVos’s telling, abortion is an evil akin to slavery, placing those who support legalized abortion rights on a moral par with those who backed slavery in Lincoln’s time.

She made her remarks at a dinner sponsored by Colorado Christian University. The event was closed to the press but attended by a reporter from the Colorado Times Recorder, who first reported DeVos’s comments.

Her comparison was sharply challenged Thursday by abortion rights supporters.

“To compare anything to slavery is to devalue America’s greatest crime and those who endured. Repulsive,” Rep. Katherine M. Clark (D-Mass.) said on Twitter. Another Massachusetts Democrat, Rep. Ayanna Pressley, wrote: “As a Black woman & the Chair of the abortion access task force, I invite you to come by the Hill and say this to my face. Would welcome the opportunity to educate you.”

DeVos is just the latest public official to make the comparison. Earlier this month, Utah Lt. Gov. Spencer Cox compared abortion to slavery, saying future generations will come to see abortion as negatively as people view slavery today.

In 2017, Judge John K. Bush came under fire when he was nominated to the U.S. Court of Appeals for the 6th Circuit for a blog post comparing slavery and abortion. “The two greatest tragedies in our country — slavery and abortion — relied on similar reasoning and activist justices at the U.S. Supreme Court,” he wrote. He was narrowly confirmed by the Senate, with opponents citing these views, among others.

The comparison between abortion and slavery dates back to at least the mid-1970s, as abortion opponents were forming legal and rhetorical strategies in the wake of Roe v. Wade, the landmark 1973 Supreme Court ruling that barred states from outlawing abortion services.

Almost immediately after the case was decided, the antiabortion movement identified with the abolitionist movement that worked to end slavery, said Mary Ziegler, who studies the history of the abortion debate at the Florida State University law school.

She said abortion opponents, in the aftermath of Roe, sought to amend the 14th Amendment to the Constitution, which was adopted following the Civil War and the end of slavery. The amendment guarantees all persons due process and equal protection under the law. Abortion opponents wanted the text to define persons to include fetuses still in the womb.

To that end, they linked the rights of the fetus to the rights of slaves, Ziegler said.

“It made a lot of sense to draw on the abolitionist movement,” she said. “The movements were spiritually linked from the beginning.” Antiabortion activists have also at times compared their cause to the more recent campaign for civil rights for black Americans.

Abortion was not an issue when the 14th Amendment was under discussion. At the time, abortion was culturally acceptable and widespread, Ziegler said, although there were efforts underway to criminalize the procedure in some states.

In her speech Wednesday, DeVos, who attended a Christian college, said the administration is working hard to provide a role for religion in education by, for example, reinforcing the right of students to pray in school. Earlier in the day, she was at the Supreme Court when justices heard arguments in a case considering whether a state can exclude religious schools from a taxpayer-supported scholarship program.