Emancipation (1862) was closely tied to growing power of abolitionists as McPherson says:
By the beginning of 1862 the impetus of war had evolved three shifting and overlapping Republican factions on the slavery question. The most dynamic and clearcut faction were the radicals, who accepted the abolitionist argument that emancipation could be achieved by exercise of the belligerent power to confiscate enemy property. On the other wing of the party a smaller number of conservatives hoped for the ultimate demise of bondage but preferred to see this happen by the voluntary action of slave states coupled with colonization abroad of the freed slaves. In the middle were the moderates, led by Lincoln, who shared the radicals' moral aversion to slavery but feared the racial consequences of 
wholesale emancipation. Events during the first half of 1862 pushed 
moderates toward the radical position. One sign of this development was the growing influence of abolitionists. "Never has there been a time when Abolitionists were as much respected, as at present," rejoiced one of them in December 1861." [End quote from page 494