One of the best chances the Union had for a victory that was missed was at Petersburg in 1864 when the Union army could have marched into Richmond behind Robert E. Lee and forced him into a battle he would inevitably have lost in open terrain against superior numbers and firepower where *Grant* chose the terrain first.
If this happens, to be certain Lincoln wins re-election by a landslide, but does a Grant victory over Lee in June of 1864 quite mean the end of the Confederacy the way it did in April 1865? At this point Johnston is by no means near defeat by Sherman and is effectively the most significant Confederate leader left. Would a defeat of the ANV mean he immediately gives up the Ghost?
Obviously the North still wins but what happens if the Union takes Richmond in mid-1864 just as Lincoln's nominated for re-election? Given that in 1864 his re-election in wartime wasn't a given, what would the domestic political butterflies be?