I believe that if the seceding states held referenda, and by majority vote of all of their residents, both slave and free, voted to secede, the union would have let them go their own way. Of course the states with few slaves, like Virginia, only had a slight white majority for secession, and states where whites were strongly desirous of secession, like Alabama, Georgia, Mississippi, and South Carolina, whites were a minority of the population.
Not exactly.The referendum, held 23 May 1861, confirmed the convention's Ordinance of Secession by a vote of 132,201 to 37,451. Most other referenda had similar or wider margins.
Of course, that was on 23 May, and VA had already been at war with the Union for more than a month. Had the vote been held in early April or before, the results would have been quite different.
states where whites were strongly desirous of secession, like Alabama, Georgia, Mississippi, and South Carolina, whites were a minority of the population.
Partially true. I believe slaves were a majority only in MS and SC, although the numbers were close in most of the Deep South states. Given the large numbers of free blacks in LA, it may have had a black, though not slave, majority.
http://www.sonofthesouth.net/slavery/slave-maps/slave-census.htm