Presidential historian Jon Meacham compared President Biden to Abraham Lincoln Tuesday, arguing the upcoming midterm elections will be the most important choice that America has made since the lead up to the Civil War. 

Appearing on "CNN Tonight" to promote his new book about Lincoln, he was asked by CNN co-host Alisyn Camerota to "tell us why you think that this is the most important election since 1850." 

Meacham responded that the upcoming elections are about a lot more than just particular policies.

"Well, I think it's the most important election easily since that period because we are facing a stress test for the rule of law and democracies run not just on policies, not just about what a particular policy or tax rate is, it's about an overall context of our mutual respect for each other as fellow citizens and a sanctity of law and custom that means that people who win elections legitimately get to serve in office," Meacham said. 

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Meacham, who spoke at the 2020 Democratic National Convention, went on to mock former President George W. Bush while criticizing the Republican Party. 

"When you deplete the trust in the system, which is what is unfolding today around the country, and I will confess, as George W. Bush might say, I misunderestimated the power of the 'big lie' here, but it's burrowed in and democracies do not long endure if everything becomes about power at the expense of winning humbly and losing graciously," Meacham said. 

Co-host Laura Coates brought up the Confederacy and slavery before the Civil War and how Meacham compared them to Republicans who question the 2020 presidential election, noting how he wrote that both Lincoln and Biden had to deal with their own versions of the big lie, with Lincoln's being that "slavery was a justifiable institution."

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She said there were moments where, if Lincoln had succumbed to pressure to placate the Confederacy, history would have turned out much differently and told Meacham, "You draw these analogies in a way, I think is not always so obvious but it's fascinating to think of how and where we are today."

Meacham said the main question we must answer "for the continuation of the constitutional experiment" is "do we put our own interests above everything else?"

"If we go entirely political, if it's entirely - every moment is this battle where it is cataclysmic - then the system doesn't endure," he said, reiterating that Lincoln could have chosen a different path. But because he prioritized democracy over his political future, "Abraham Lincoln, flawed, fallen, and fallible, said no. And he said no, because he believed fundamentally that slavery had to die and the union had to endure."

Republicans are gaining ground in the crucial midterm elections, with Republicans focusing on the economy and rising crime while Democrats have sought to make the campaign about abortion and a "threat to democracy."