What was the key to Abraham Lincoln's reelection?

In the midst of the American Civil War, incumbent President Abraham Lincoln of the National Union Party easily defeated the Democratic nominee, former General George B. McClellan, by a wide margin of 212–21 in the electoral college, with 55% of the popular vote. Lincoln's re-election ensured that he would preside over the successful conclusion of the Civil War. Lincoln's victory made him the first president to win re-election since Andrew Jackson in 1832, as well as the first Northern president to ever win re-election.

Explanation:

a historian who compares the expansion of political systems to the expansion of economic systems to the expansion of economic systems is organizing history by theme.

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