What is the historical precedent for a president stepping down?

The messaging from the White House right now is clear: President Biden will stay in the race. But if he did make the difficult decision to withdraw, there is precedent for it. Amid the racial and social turmoil of the 1960s and the Vietnam War, President Lyndon B. Johnson did just that.

Scripps News spoke with Kevin Boyle, a professor of American history at Northwestern University who's written about the parallels between the situations facing both Presidents Johnson and Biden in a recent op-ed for The New York Times.

"The really critical comparison in my mind is that Johnson withdrew from the race in March 1968 for a lot of complicated reasons — personal reasons, political reasons," Boyle said. "But at the heart of it, what he was trying to do was to solve this huge complex of escalating crises. He was trying to defuse what he saw as a huge fundamental threat to the United States. That's what he thought he could accomplish by stepping out of the race. And I think that in many ways Joe Biden faces a deeper, more existential threat to the nation that even Johnson did. I think that's where the comparison is: That stepping down for Biden would be and act of sacrifice, of self sacrifice, for the good of the nation."

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"What Johnson faced was a combination of a war in Vietnam that was spinning rapidly out of control, a party that was splintering around him and a financial crisis — a global financial crisis he needed to defuse," Boyle said. "Those are huge, huge things. I'm not trying to minimize those. But what Biden faces in my view, is the threat to the democracy itself that comes with the reelection of Donald Trump."