Do they mention the support of James Buchanan and other Democrats for an upward revision of tariffs to pay for the deficit? Regardless of what we think about the economic wisdom of this, a modest increase in tariff rates was apparently a relatively uncontroversial proposal in the early Buchanan administration.
You have apparently misread my comment. I was refering to the fact that some upward revision of the tariff was bound to happen and would not have been controversial. Because of the strains over slavery and his own weakening grasp on power, Buchanan lost control over the process. The result was higher increases in tariffs. But had the political environment remained calmer and more stable, it's likely that more moderate increases in the tariff would have come and been accepted by most politicians, North and South.
Had Southerners really wanted to block tariff increases that they regarded as excessive, they could have used the Senate rules of the time to filibuster the tariff bill. It required a two-thirds vote to cut off debate, and it's extremely unlikely that the Republicans could ever have gotten this -- certainly not without substantially scaling back their demands. But the Deep South was already set on secession, and the tariff was put on the backburner.
If you have access to a university library, you might take a look at "Incidental Protection: An Examination of the Morrill Tariff" in "Essays in Economic and Business History."
Also, this PDF article "Imagining 'a Great Manufacturing Empire': Virginia Secessionists and the Possibilities of a Confederate Tariff" presents a very different view of tariffs in the Confederacy.
Okay. I don't agree that it was bound to happen, but I suppose it is possible that a slight tariff hike could have been done with minimal controversy. This was not the case of what happened though.
Had Southerners really wanted to block tariff increases that they regarded as excessive, they could have used the Senate rules of the time to filibuster the tariff bill.
Strategically that is entirely possible to push off the tariff, but for indefinate sustainability across four years it is simply not practical or realistic. The cards were heavily stacked against any limited effort that could be mounted in the Senate.