U.S. Education Secretary Betsy DeVos ignited a fiery debate this week around whether the choice to allow slavery compares to the choice to have an abortion.

The controversy came after a speech she gave at a Christian college before the March for Life in Washington, an annual event for anti-abortion activists that draws thousands of people. Friday, the event featured a speech by Donald Trump, the first sitting president to address the marchers.

Evangelicals make up an important part of Trump's base in this election year, and DeVos, a conservative Christian, has been one of his longest-serving top Cabinet members. She's the latest in a long line of politicians and activists who have tried to make connections between slavery and abortion rights, to the dismay of some historians.

DeVos spoke at Colorado Christian University on Wednesday about opposing abortion rights, advocating for religious freedom and supporting faith-based schools. She invoked President Abraham Lincoln, according to prepared remarks provided by her office.

DeVos said Lincoln essentially dealt with a "pro-choice" argument of his day around slavery. Lincoln held the position, DeVos said, that states "choosing" to allow enslavers or to prohibit them should know slavery was viewed by many Americans as a vast moral evil.

"Lincoln was right about the slavery 'choice' then, and he would be right about the life 'choice' today," DeVos said.

U.S. Rep. Ayanna Pressley, D-Mass., who is black and heads an abortion access task force, challenged DeVos about that comparison in a tweet Thursday.

"The rhetoric & policies of anti choice zealots like DeVos put the lives & bodily autonomy of far too many people at risk," Pressley wrote.

A spokeswoman for DeVos countered Friday that the secretary did not compare abortion to slavery.

"She made clear that the 'choice' debate over states' rights was as morally bankrupt as the abortion argument about the so-called 'right to privacy' is," spokeswoman Angela Morabito wrote in an email to USA TODAY.

DeVos, Morabito said, alluded to the famous debates between Lincoln, a Republican, and Stephen A. Douglas, a Democrat, in 1858. (Lincoln challenged Douglas for his seat in the Illinois Senate.) Those debates, Morabito said, were "a critical turning point for the nation, in which human dignity ultimately won out by confronting the underlying moral question."

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Social media lit up Thursday and Friday as people supported or castigated DeVos for her remarks.

People on both sides of the abortion debate have used slavery to support their positions, academics said.

"Ironically, both anti-abortion and pro-choice advocates have used slave metaphors in legal arguments in cases and law review articles dealing with abortion," Debora Threedy, a retired University of Utah law professor, wrote in a paper in 1994.

Supporters of abortion rights may draw parallels between a woman denied access to an abortion and an enslaved person unable to make decisions about her own body. Anti-abortion activists may compare a fetus in a terminated pregnancy to enslaved people who were denied their rights.

Manisha Sinha, a scholar on the history of slavery and the Civil War who teaches at the University of Connecticut, said it's "really egregious and absolutely wrong" when fundamentalist Christians and evangelicals connect their opposition to abortion to the abolitionists' opposition to slavery in the 1800s.

Abolitionists, Sinha said, tended to be very supportive of women's rights.

"Pro-choice activists have a better historical ground to invoke the abolitionists and their opposition to slavery than Betsy DeVos and pro-life people," Sinha said.

Education coverage at USA TODAY is made possible in part by a grant from the Bill & Melinda Gates Foundation. The Gates Foundation does not provide editorial input.