How did events on the battlefield effect lincoln's reelection?

Lincoln wanted to break the will of the South.

The 1864 election was the first time since 1812 that a presidential election took place during a war. For much of 1864, Lincoln himself believed he had little chance of being re-elected. Because of this, McClellan was thought to be a heavy favorite to win the election.

explanation:

may i ask what challenges?

answer; interpreting someone's past consistent with present deviance;