I believe the raw numbers of slaveholders as a percent of the population severely underestimate how widespread the institution really was, and therefore how much social and political power slaveholders would have in the semi-democratic racially based republics of the antebellum South. For example, in Mississippi only 3.91% of the total population of the state owned any slaves; in South Carolina, it was 3.79%. (All numbers are taken from the 1860 census data at the United States Historical Census Data Browser.)
But remember, in Mississippi in 1860, 55.18% of the population were slaves, who didn’t even own themselves, let alone anything else; in South Carolina, it was 57.18%. Obviously, they didn’t let the slaves vote on secession. Also, at that time women could not vote and had no voice in political affairs, except for whatever moral suasion they were able to bring to bear on their husbands, fathers, brothers, sons, etc. Finally, children–even white male children–could no more vote then than they can today.
A more accurate picture of the extent of the slaveholding class is to take slaveowners (that is, all persons owning at least one slave) as a percentage of white males over 21.
A few caveats:
[ul]
[li]The census data for adults goes by decades; I’ve taken the summary of “no. of white males, 20-29 years of age” through “no. of white males 100 years of age and over”. I think the age of majority would have actually been 21, not 20, so that will introduce some inaccuracy proportional to whatever the number of 20 year old white males was.[/li]
[li]I’m sure there were at least some female slaveholders; widows and such.[/li]
[li]Finally, there were some free blacks who owned slaves; I believe this was most prevalent in Louisiana.[/li][/ul]
That said:
Slaveholders as a percent of the total adult white male population-
In the seven “Deep South” states which seceded before Fort Sumter:
South Carolina - 39.26%
Mississippi - 37.23%
Georgia - 31.05%
Alabama - 28.46%
Florida - 27.57%
Louisiana - 22.45%
Texas - 20.63%
In the four “Middle South” states which seceded only after the outbreak of war forced their hand:
North Carolina - 24.21%
Virginia - 22.21%
Tennessee - 19.48%
Arkansas - 15.57%
In the four “Border States” which did not secede:
Kentucky - 17.75% (claimed by the Confederacy)
Maryland - 10.74% (martial law declared)
Missouri - 9.08% (claimed by the Confederacy)
Delaware - 2.62%
In no state were slaveholders an absolute majority of the electorate, but if thirty or forty percent of the voting population shares a common interest, that’s a very strong voting block in a republic. Bear in mind also that the non-slaveholders would not necessarily have been opposed to slavery or in favor of abolition. Non-slaveholders were not permanently barred from ever acquiring slaves; many may have hoped (whether or not those hopes were realistic) to own slaves at some point, just as Americans have always tended to have dreams of bettering their economic status. Non-slaveholders may still have had an economic interest in the slave economy, just as in East Texas real estate agents, owners of Cadillac dealerships, and sellers of cowboy hats may all have an interest in the price of oil. Finally, given that in some states (Mississippi and South Carolina) slaves were an absolute majority of the total population; and throughout the Deep South, slaves were nowhere less than 40% of the total population (with the exception of Texas, where slaves were only about 30% of the population), many non-slaveholding whites had deep fears about the prospect of abolition based on economic and social interests (not wanting to compete with a suddenly emancipated black population on an equal basis), and simple outright racism. The slaveholding class certainly encouraged these fears. (See for example Governor Joseph Brown’s Open Letter to the People of Georgia.)
The proportion of slaveholders in a given electorate even seems to correlate pretty well with the intensity of secessionist feeling; South Carolina, with the greatest proportion of slaveholders (as well as the largest proportion of its population enslaved) seceded first, and had long been known as a hotbed of pro-slavery and pro-secession. Mississippi, where slavery was nearly as pervasive as in South Carolina, was the second state to secede. Most of the remaining early seceders had slaveholding classes which constituted around 30% of the electorate; outliers to some extent were Louisiana and Texas, but in Louisiana although slave ownership was not as widespread in the electorate as in other Deep South states, slaves still constituted 47% of the total population, which is pretty high even for a Deep South state, and which one would expect to cause considerable fear of abolition even among non-slaveholding whites. In Texas, only 30% of the population was enslaved, and only 20% of so of the population were slave owners, yet the state was an early seceder. By contrast, in North Carolina, nearly a quarter of the electorate owned slaves, and a third of the state’s population was enslaved, yet the state was the last of all the states to secede. I don’t know that North Carolina’s reluctance to leave the Union reflected any widespread abolitionist sentiment there, though–many Southerners were ardently pro-slavery and still anti-secession, arguing (correctly, as it turned out) that secession would be disastrous for the institution of slavery.