Final answer:
Ulysses S. Grant is the hero at Vicksburg who became the commander of all Union armies in 1864. He led Union forces to significant victories and ultimately against General Robert E. Lee's Confederate army. General George McClellan was Abraham Lincoln's opponent in the 1864 Presidential election.
Step-by-step explanation:
The hero at Vicksburg, who became commander of all Union armies in 1864, is Ulysses S. Grant. The Vicksburg Campaign was critical to the Union's success and General Grant's effective strategy helped secure this victory. In terms of recognizing commanders in other significant battles, it's important to note that General Grant was also the Union commander at the Battle of Shiloh, and he is known for relentless campaigns against Confederate forces, particularly those led by General Robert E. Lee. As for the 1864 presidential election, it was General George McClellan who ran against President Abraham Lincoln.