Quoted:
The South could have never won in a slugging match. The only hope was Lee's success at routing the Union armies and getting into Washington to force an end. That hope ended in 3 days in July 1863 at Gettysburg. If Lee would've listened to Longstreet, there would have been nothing between the army of Northern VA and DC. The game would have been over.
Nice try. Even if Lee could have beaten Meade or Hooker (who both he and Jeff Davis thought he was going to fight.) and had enough power left to go to Washington. He could not have beat the Army of the Potomac sufficiently bad enough to allow him room and time AND still have enough troops to successfully assault the lines of defences around Washington before the North could have restored a larger Army in the field than he had and would have hammered him to pieces between them and the forts.
Lee had no reinforcements. His supply train was what he had with him. Any supply train from VA would never have reached him Meade had approximately 10 times the number of wagons as Lee had waiting for him at the Pipe Creek Line where he had planned to make his stand, drawing Lee into a massive trap. Meade also had several RR lines into his rear from Philly, NYC and Baltimore. Lee had none. Had Meade moved to the Pipe Creek line Lee would have been caught on the horns of a dilemna. Attack a numerically stronger force in a stronger position and an interior position at that. That attack would have been necessary in Lee and Davis's minds to accomplish what both Lee and Davis hoped to accomplish by going North. Throw his army away to accomplish the mission (hopefully) or save his army and get the hell out while he could.
Lee went North, not primarily to invade the North, not primarily to try to destroy the Army of the Potomac or to take Washington, although any or all of those would potentially been the trigger to get the desired result. What was that? Cause the North to pull enough troops away from Grant on the Mississippi to stall or cancel the Vicksburg Campaign. Why? Because everybody knew that when Vicksburg fell the river fell and when the river fell the western half of the CSA was gone. Didn't work. Grant was never asked to release troops, Lee had to go after Meade and not Hooker, Lee barely got his Army away. There was never another offensive campaign of any strength by the South after July '63.
If Lee had been focused on attacking and taking Washington, he would have had a very similar challenge to what Grant was facing. Going after a well fortified city on the other side of a major river. With one advantage ONLY. North of Washington the river was such that it could be crossed at several fords or with pontoon bridges. South of the city was not only well and strongly defended the river could not be crossed without a major amphibious effort. the south had NO capability of mounting an amphibious campaign of any size, let alone one that could have had any hopes of success against the Union forces in the Potomac and Chesapeake. Pemberton and Johnston were trying to get reinforcements to Vicksburg, not only none worth mentioning to be had, but only one rail line in. Meade/Hooker had several rail lines to assist in the protection of a DC front and lots of reinforcements available.
The only Border State who could have made a difference was Maryland.
Major error by the South there, Sumter was a political feature of no real strategic significance to either side. the south should have put all it's efforts into peeling Maryland away from the North or isolating Washington and forcing the government to leave. All shelling Sumter did was give Lincoln a major rallying point. Seal the channel and passively prevent supplies and Sumter surrenders quietly.