Victory for the Confederacy, as of May 1863, is still possible, indeed likely, if more battlefield victories lead to the election victory of a "peace candidate" like Democrat George McClellan in November 1864.
As of "today" neither Lee nor Davis have decided what they want to do next.
On the one hand, there is the matter of strategically vital Vicksburg, Mississippi, and that drunk of a Union general, might he just stagger into victory there?
Naw... Pemberton & Joe Johnson have that under control, right?
OK, we'll reinforce Johnson, send him the Confederate divisions of Loring & Walker, plus WH Jackson's cavalry, then Breckenridge & French's divisions.
That gives old Joe 36,000 plus Pemberton's 30,000 at Vicksburg, should be plenty enough to defeat yet another drunken Union general, right?
So, there's no need to send Lee to Vicksburg, or even, say, Longstreet, to add his corps and take command, is there?
Old Joe Johnson can handle it, so let's keep Lee in the Virginia and plan something that will really strike fear in the hearts of Union voters -- let's invade the Union!
Notice here, if the railroads are in good condition, in a matter of days, a week at most, Longstreet's corps could be transfered to the Vicksburg theater.
As for whether a Confederate victory would save the United States, here's one vision of what that might look like:
