What started with a single question from a voter about the origins of the Civil War has morphed into a sprawling political clash over a monumental event in American history, making the Civil War a major component of a presidential election for the first time in recent memory and exposing fresh divisions over race, history and progress.

Since former U.N. ambassador Nikki Haley did not mention slavery when asked two weeks ago what sparked the conflict that tore apart the nation from 1861 to 1865, every major presidential candidate has weighed in on it. Their commentary sheds light on how each party is addressing long-standing divisions over the legacy of its most divisive period - and what they mean for the current battles over race in America.

Republicans often downplay the worst components of the Civil War era, arguing that the country has moved far beyond its earlier sins and does not benefit from resurfacing them. Democrats, by contrast, see an integral tie between America's history of racism and its modern-day reality, and draw very different conclusions about what is needed to address that history.

"The Civil War has never really left American politics - it just seems to have exploded in this moment," said Tim Galsworthy, a historian at Bishop Grosseteste University who is writing a book about the Republican Party and memories of the Civil War. "When the U.S. is divided, the Civil War becomes that great reference point, because it's the ultimate moment of division."

The subject is especially volatile now, with the issue of insurrection back in the spotlight for the first time in 160 years. Some of former President Donald Trump's adversaries are seeking to disqualify him for trying to overturn the 2020 election, while his supporters are downplaying the seriousness of the Jan. 6, 2021, assault on the U.S. Capitol, portraying it as a heroic battle against injustice.

In recent days, those divisions have been laid bare by presidential candidates' decision to train their attention, even briefly, on the past rather than the future. Trump alleged the Civil War could have been avoided through negotiation, a notion almost unanimously rejected by historians. Florida GOP Gov. Ron DeSantis slammed Haley for omitting slavery as a factor in the war, but he faces scrutiny over his own efforts to restrict how slavery and its legacy are taught in schools.

President Joe Biden, meanwhile, eagerly joined the fray, using the debate over the Civil War to make a broader case that Trump and his election denialism represent a threat to the nation reminiscent of the Confederacy and its aftermath.

"Let me be clear for those who don't seem to know: Slavery was the cause of the Civil War," Biden said during a campaign event Monday at Mother Emanuel AME, a historic Black church in Charleston, S.C. "Now we're living in an era of a second Lost Cause. Once again, there are some in this country trying to turn a loss into a lie."

Imagery from the Jan. 6 attack and a 2017 white-supremacist rally in Charlottesville - both of which have featured prominently in Biden's presidential campaigns - provide explicit echoes of the Civil War. The Charlottesville rally erupted over plans by the city to remove a statue of Confederate Gen. Robert E. Lee, while the Jan. 6 insurrection featured a Confederate flag brandished through the Capitol by a rioter.

But it was a December town hall in New Hampshire that brought the issue to the heart of the Republican presidential primary.

"What was the cause of the United States Civil War?" a voter in Berlin, N.H., asked Haley, a former South Carolina governor who has staked much of her presidential bid on a strong performance in the Granite State.

Haley fell back on an assertion that has historically been seized upon by people sympathetic to the South - that the war was not fundamentally about slavery, but about federal power.

"I think the cause of the Civil War was basically how government was going to run, the freedoms and what people could and couldn't do," Haley said, before continuing on to discuss in broad terms the importance "of the role of government and what the rights of the people are."

The man who asked the question, who refused to give reporters his name or party identification, told Haley that he was surprised she did not mention the word slavery. "What do you want me to say about slavery?" Haley said.

Historians have long concluded that Southern states' desire to preserve and expand the institution of slavery was the driving force behind a war that led to the deaths of at least 620,000 Americans. It was emphasized in numerous speeches by leaders on both sides at the time.

Haley acknowledged as much a day after the town hall following a torrent of backlash from Democrats and Republicans alike. She told a local radio show that "of course the Civil War was about slavery."

While politicians on both sides agreed that Haley's initial answer was deficient, the dust-up laid bare other disagreements about the war, its antecedents and its aftermath.

DeSantis, who once taught history at a high school in Georgia, bashed Haley for answering with an "incomprehensible word salad," adding that slavery was obviously at the heart of the war. But he quickly came under fire from critics who argued that his state has been aiming to downplay the horrors of slavery and limit how America's racial history is taught in schools.

DeSantis, whose "anti-woke" agenda has put Florida at the forefront of a nationwide effort to restrict certain books and approaches to teaching about race, last year supported a set of standards for middle school instruction that included teaching "how slaves developed skills which, in some instances, could be applied for their personal benefit."

Many historians criticized the standards, which also noted that other countries enslaved people as well, as an effort to soften the brutal reality of slavery in the United States.

Trump also mentioned slavery while discussing the Civil War this month, but only in passing. Instead, he focused his commentary on what he described as Abraham Lincoln's failure to avert the war through negotiation.

"The Civil War was so fascinating. So horrible. It was so horrible but so fascinating. ... I'm so attracted to seeing it," he said in Iowa on Jan. 6. "So many mistakes were made. See, there was something I think could've been negotiated. I think you could've negotiated that."

Historians note that multiple attempts at compromise were made in the run up to the Civil War and that negotiations came to an impasse over irreconcilable differences over slavery.

The former president did not offer specifics on what kind of negotiation could have headed off the war. His rhetoric has resonated with conservative voters unhappy with what they see as misguided efforts to link historic wrongs to current inequities and demand reparations for long-ago injustices.

Trump has criticized the Black Lives Matter movement for seeking the removal of Confederate statues from public spaces, accusing activists of trying to erase history, an allegation they have often leveled at him. He has also opposed the push to rename military bases named after generals who fought for the Confederacy.

Haley, for her part, has pointed to her efforts as governor to remove the Confederate flag from the grounds of South Carolina State House in 2015. The move came after a white supremacist murdered nine Black churchgoers at Mother Emanuel church and photos emerged of the killer posing with the Confederate flag.

"When we turned around and had the worst shooting in a religious place that we had seen in this country, not only did I pass the first body camera bill in the country and keep our state together, not only did I move to bring the Confederate flag down, we came together as a state," Haley said Wednesday at a GOP presidential debate.

South Carolina, the first state to secede from the Union in 1860, has become a key locale for Democrats in recent days, as top figures have flooded the state ahead of its Feb. 3 Democratic presidential primary. For Biden and Vice President Kamala Harris, the state has become a venue for outreach to Black voters, who some polls suggest have become less than enthusiastic about the president's reelection.

On Monday at Mother Emanuel, Biden accused Republicans of "trying to steal history," which he contrasted with his own efforts to "make history" by fighting for equity.

Two days earlier, Harris was in Myrtle Beach, S.C., where she spoke at a Black church and accused GOP extremists of trying to "erase, overlook and even rewrite the dark parts of America's history," adding, "for example, the Civil War, which must I really have to say was about slavery?"

The president has made a direct appeal to Black voters, some of whom have been concerned by efforts to restrict books and revise history as well as moves to roll back voting rights and affirmative action. Biden has made the case that Trump, who is gaining support among African Americans in some polls, presents a grave threat on these and other issues important to Black voters.

"Anyone negotiating over slavery - the indisputable cause of the Civil War - is contributing to the poison of white supremacy that has infected the MAGA Republicans running for president," said Michael Tyler, communications director for the Biden campaign. "It's a sad and unsurprising reminder of how extreme and out-of-touch Donald Trump and his friends are with the American people."

But the push has opened up Biden to critiques of his decades-long career in public office, in which his handling of race issues has at times drawn scrutiny. In recent days, Haley's campaign has highlighted the president's own history, noting his positive relations with senators who supported segregation.

"I don't need someone who palled around with segregationists in the '70s and has said racist comments all the way through his career lecturing me or anyone in South Carolina about what it means to have racism, slavery or anything related to the Civil War," Haley said at a Fox News town hall Monday.

The bickering highlights how the country lacks the kind of unifying voice that can break through the noise in deeply divisive times as Lincoln did in the 1860s, said Tevi Troy, a senior fellow at the Bipartisan Policy Center.

"The other side of the Civil War discussion is that despite the trauma and the great cost, the nation survived, thanks to Lincoln's leadership," said Troy, whose book "Shall We Wake the President?" focuses on presidential leadership in times of crisis. "The interest in the Civil War reflects these twin concerns, about both political disagreement and the absence of wise leaders who can navigate us through these challenging times."