My guess is Lee would probably try to secure Baltimore, and by extension, Maryland in order to shift the front north, away from Virginia. Whether it works is a different question entirely.
Lee's army was on a very tenuous supply line, and without another quick victory, he'd be forced to retreat in order to avoid being cut off. McClellan would almost certainly be sacked permanently, and with a Confederate army in Union territory, the Emancipation Proclamation will probably be delayed or butterflied away. McClellan would also lack the credibility to run for President, and whether Lincoln gets unseated depends on what happens after Sharpsburg.
The Union will probably win the war in the long run unless Lee continues to roll sixes.
Lee's army was on a very tenuous supply line, and without another quick victory, he'd be forced to retreat in order to avoid being cut off. McClellan would almost certainly be sacked permanently, and with a Confederate army in Union territory, the Emancipation Proclamation will probably be delayed or butterflied away. McClellan would also lack the credibility to run for President, and whether Lincoln gets unseated depends on what happens after Sharpsburg.
The Union will probably win the war in the long run unless Lee continues to roll sixes.