Actually with representatives, no. The southern representatives were all there when the Morrill bill was voted on in May 1860. All but one of them voted against it, whereas all but some 5-6 yankees voted for it.
Do they mention the support of James Buchanan and other Democrats for an upward revision of tariffs to pay for the deficit?
They do mention the northern Democrats support of it as a sectional thing, as well as the southern one's opposition. They also look at the rates some and point out it's schedule contained revenue measures but also protection measures, found in the higher end rates of the schedule.
a modest increase in tariff rates
The problem is it was not modest at all. They literally doubled the rates from 1861, which had been the low rates in place from the late 1850's, to 1862 after the Morrill bill. The average rates went from 18% to 36%.
was apparently a relatively uncontroversial proposal
All indications are that it was anything but and drew sharp sectional opposition from the south in near unanimaty.
Congressman Keitt of South Carolina left at Christmas 1860.
Walt
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.