Manisha Sinha is the Draper Chair in American History at the University of Connecticut and the author of " The Slave's Cause: A History of Abolition ". The opinions expressed in this commentary are hers. View more opinion articles on CNN.

(CNN) Donald Trump likes to compare himself to Andrew Jackson, but the Andrew he really resembles is Andrew Johnson. What they have in common are delusions of personal grandeur and a tainted ascent to the presidency. Trump was elected by a minority of the American electorate, with help from the vagaries of the Electoral College system and from considerable Russian interference.

Manisha Sinha

Johnson became president thanks to an assassin's bullet. While Johnson immodestly compared himself to Jesus and Moses, Trump claims he is the best at everything, even boasting recently on Twitter that his popularity among Republicans exceeds that of Abraham Lincoln.

Indeed, pundits have likened today's partisan divisions to those of the Civil War era. But they more closely resemble the politics of Reconstruction, the period after the war when for the first time in history, an American president, Johnson, was impeached by the House of Representatives.

But the resemblance between the two men goes deeper. Johnson's white-supremacist views were blatant and his policies precipitated a constitutional crisis that put the President at loggerheads with Congress and his own party, the Republicans.

(Remember that everything you know about Republicans and Democrats today should simply be flipped for the 19th century. The Republican Party then was the liberal party of anti-slavery, big government and Lincoln. The Democrats were the party of white supremacy, Southern slaveholders and states' rights. In the 20th century, after the New Deal and civil rights movement, the parties exchanged ideological roles.)

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