Well it was in the context of @SunUp post, in that he wanted to build quantitative data of who supported secession and etc, I said that I am not entirely sure that data exists. We did gather some data like that at the time, but in a way more flawed than modern opinion polling, and records also are more scarce than in modern times. Only three states had referenda on secession, it was generally implemented by State legislatures or special conventions, who we can presume had the support of their constituency, at least those constituents who had voted for them, but that’s an imperfect level of understanding. Hence my comment that I’m not really sure we can know in a real numbers sense.
We do know that the elements that ran Southern society were in favor of secession, and a non-trivial number of its adult men volunteered to fight and die to try to achieve it–although even that is a little imperfect, as I’ve read accounts of Confederate soldiers who were not in favor of secession, but felt an obligation to fight for their State in a shooting war, even if its war aims didn’t line up with their own preferences–I do think we can assume most who went to fight for the CSA were pro-secession, though–but even then that’s just a subset of adult males.
The South Carolina secession convention is somewhat of an interesting look at the situation. The South Carolina General Assembly called for the convening of a secession convention, delegates to that convention were elected. A total of 169 delegates were sent, my understanding is that 153 of them were slaveholders, with over half of them being “significant” slaveholders of large numbers of slaves. But the thing is I’m not really sure in the selection of these delegates if the voters had any real choice. I think a lot of these delegates ran unopposed, and I think where they didn’t it was more selecting which pro-secession person you wanted to send as your delegate. I’m not really sure it was structured for anti-secession South Carolinians to have a voice, and I suspect many just did not participate in the process at all, seeing it as invalid.
In Mississippi the secession convention appeared to have been more openly contested, with something like 15 of the delegates out of 105 or so voting not to secede.
Florida’s secession convention had 69 delegates (all of whom owned at least 10 slaves), 7 nay votes–they held no debate on whether to secede or not, only when and what text should be in their secession declaration.
Alabama had a 100 delegate secession convention, my understanding is they were not elected on secession or unionism, but “immediate secession” or “cooperative secession”, the latter simply meaning the position that they would be willing to secede in cooperation with a number of other neighboring states i.e. they did not want Alabama seceding by itself. A number of the cooperative secession delegates joined in with the immediate secessionists (who had 53 seats) to pass the secession ordinance due to the fact South Carolina, Mississippi and Florida had already finished seceding by the time the Alabama convention voted.
Georgia’s secession convention is one of the few I find documentary evidence of actual Unionist candidates standing for–and winning, delegate positions, and one of the few secession conventions that actually debated whether to secede or not vs when and how to secede, the Georgia convention met for a lengthy period of time, and despite some early estimates of it being a close vote among the delegates, there was a shift as the previous four states passed secession ordinances and the convention ended up voting for immediate secession via a strong margin–interestingly Georgia’s secession convention then immediately converted to a constitutional convention to redraft the Georgia State constitution.
Skipping over several of the other states with more or less similar histories,Texas’s secession is somewhat interesting. Its governor Sam Houston was an ardent unionist, and was not willing to call the legislature into special secession initially. He only ultimately relented when it became obvious the citizens were simply going to form their own secession conventions in spite of him if he did not. The Texas legislature as in the other states established for the election of delegates to a secession convention. We know that these elections would not meet any modern standards of democracy. Unionists were strongly discouraged from attending, and selection of delegates was usually via a “voice vote” at a public meeting house, where any Unionists who dared attend or speak out were subject to assault or worse if they raised objection. Given this voting method was strong armed by secessionists, it is unsurprising that Texas had the strongest margin for secession in its convention other than South Carolina (which had a unanimous vote.) The Texas secession convention unlike most of the other states, did put approval of the ordinance up to a referendum, which passed 46k to 13k, but voting in that referendum was ripe with all the same issues of voting in the convention delegation elections, this was an era before the anonymous vote, and bullying and physical violence at voting places as the norm in the middle 19th century. The fact that Texas had a pro-unionist Governor and had 13k out of around 60k votes willing to actually vote to stay in the Union suggests to me secession was probably significantly less popular in Texas than in a number of the other Confederate states in the “Old South.”
Arguably of course Virginia and Tennessee were even more divided on secession. Virginia so much so that it permanently lost its Western counties over secession, as they were enough opposed they formed their own “Restored Government of Virginia” meeting in Wheeling, that declared the Richmond Assembly invalid, and then approved the splitting of the state in two. Tennessee had a very similar movement going on with its Eastern Appalachian counties, but it was able to suppress it with martial law and heavy handed tactics–one of Tennessee’s United States Senators was an ardent unionist–Andrew Johnson, who went on to be Lincoln’s second Vice President and successor after his assassination.
Ultimately while I strongly believe a majority of free white males in the South approved secession, the evidence isn’t necessarily certain, because like everything in the old slaveocracies, it was as process dominated by, started by, ran by large slaveholding wealthy men, and anti-democratic measures were employed almost across the board to suppress any opposition to it. These were less free elections than the ones Hitler won in the final years of Weimar Germany (which themselves were certainly problematic elections.)