First, see my post #29 above.
Now, read especially what the Constitution says about "invasion," "insurrection" and "rebellion."
You'll find that Lincoln had CONSIDERABLE constitutional powers during the Civil War.
And if you ever wondered WHY those powers are there, then you might want to think back to just WHO was IN CHARGE of the Constitutional Convention in 1787. Do you remember?
That's right, it was George Washington, a man with considerable experience in all manner of problems relating to "nation building." ;-)