The factor that could be considered the most tertiary among the options listed is moral objections to slavery.
While moral objections to slavery were significant and played an essential role in shaping public opinion and fueling abolitionist movements, they were somewhat more indirect compared to the other factors. The immediate catalysts for the Civil War included more direct political actions and events, such as the political control of the agrarian economy, arguments about states’ rights, and especially the election of Abraham Lincoln in 1860, which directly precipitated the secession of Southern states.
In contrast, moral objections to slavery, while a crucial part of the broader narrative, were less of an immediate trigger for the conflict itself compared to the other contributing factors.