most consequential elections cases ever.# At issue, does the Constitution's Civil War era insurrection clause disqualify# Donald Trump from holding higher office?

The court will hear a case out of Colorado# where its state Supreme Court ruled Mr. Trump## is ineligible to be on the ballot there.

Other# states have come to the opposite conclusion.

William Brangham explains the# background to this historic case.

DONALD TRUMP, Former President of# the United States (R) and Current## WILLIAM BRANGHAM: It was a day# scarred by chaos and violenc Thousands of supporters of then-President# Donald Trump stormed the U.S. Capitol,## trying to stop the certification of Joe Biden's# victory in the 2020 presidential election.

But## was that day and the events leading up to it# an insurrection?

And, if so, does an obscure## provision in the Constitution prohibit Donald# Trump from holding political office ever again?

Those are some of the key questions# the U.S. Supreme Court will weigh## tomorrow as the justices parse a# rarely considered provision of the## 14th Amendment for the first# time in the court's history.

MANISHA SINHA, University# of Connecticut: So the 14th## Amendmen WILLIAM BRANGHAM: Manisha Sinha is a# Civil War historian at the University of## Connecticut and one of the many researchers# who submitted amicus briefs in this c MANISHA SINHA: The reason why the framers decided# to do this was because they wanted to discourage## political domestic violence, which is exactly what# is happening in the postwar South at this time.

WILLIAM BRANGHAM: Written after# the Civil War, the 14th Amendment## addresses the rights of American citizens,# particularly forme Of its five sections, it's Section 3 that's the# crux of this case.

It says, no one who took an## oath to support the Constitution can ever hold# office again if they -- quote -- "engaged in## insurrection or rebellion against the same or# given aid or comfort to the enemies thereof."

Is it clear to you that January# 6 and the events leading up to## it in that day itself constitute# any insurrection under Section 3?

DAVID BLIGHT, Yale University:# It is my opinion that it does,## but it is also very much in the historical record.

WILLIAM BRANGHAM: David Blight is a Civil War# historian at Yale.

He won a Pulitzer P for his biography of Frederick Douglass# and also submitted a brief to the court.

DAVID BLIGHT: An insurrection, if one looks up# definitions of it, is when a group of people## engage together to resist the power of the federal# government by force with a large public aim.

And what could be more important than overturning# a legitimate election?

The mob not only engaged## in violence, invaded the U.S. Capitol, broke# down its doors, broke down its windows.

It led## to deaths.

It led to all sorts of injuries.

It# is a miracle there weren't more guns involved.

JASON MURRAY, Plaintiffs' Attorney:# Who could more easily subvert our## democracy from within than a commander# WI LLIAM BRANGHAM: Last December# in Colorado was the first time## a group of voters successfully won a# case against Even though Trump's legal team argued# he was simply exercising his right to## question the election and never# urged anyone to commit violence,## Colorado's Supreme Court, in a split# decision, ruled Trump had engaged in an## insurrection and ordered him struck from# the state's Republican primary ballot.

Not long after, Maine's secretary of state# also decided on similar grounds that Trump## should be removed from that state's ballot.# The U.S. Supreme Court will now try to settle## what this 150-year-old provision means# and whether it applies to Donald Trump.

The former president's legal team will argue that# Donald Trump did not engage in an insurrection,## that Section 3 isn't applicable because# he hasn't been charged or convicted,## and that Section 3 doesn't say the president is# a -- quote -- "officer of the United States."

MANISHA SINHA: It's quite clear, both to the# creators of the 14th Amendment and those who## discussed this disqualification clause, that this# would apply to the president of the United States.## In order to be president, you have to be 35 years# of age, you have to be born in this country,## and you have to not have incited insurrection# against the government of the United States.

WILLIAM BRANGHAM: While the justices# debate these constitutional questions,## there's an equally pressing political one.

If the Supreme Court lets Colorado's ruling stand# and more states, l what will it mean for our democracy when# millions of Americans cannot cast a vote## for Donald Trump because of a constitutional# provision that few voters have ever heard of?

For the "PBS NewsHour," I'm William Brangham.