Matsui supports some interesting arguments.
"If the Army of the Potomac (the major Union force in Virginia) was dominated by generals who concurred with the ideology of the Democratic Party, the Army of Virginia was its political opposite, from its senior generals to the common soldiers. The majority of officers and soldiers in the Army of Virginia saw slavery and pro-Confederate civilians as crucial components of the rebel war effort and blamed them for prolonging the war. Ultimately, the frustrating occupation experiences of the Army of Virginia radicalized them and other Union soldiers against Southern rebellion and slavery, paving the way for Abraham Lincoln to issue the Emancipation Proclamation."I don't know. Skimming the Army of Virginia's order of battle, I don't see an exceptionally great preponderance of "radical" leaders and find it difficult to imagine the native born soldiers in the ranks of the three corps being the "political opposite" of their Army of the Potomac comrades in mid-1862. But, hey, I didn't do the research and am definitely intrigued by the notion of having my assumptions challenged on this.