I believe 12 or 13 of them had left. At least one was still there.
Again, my math may be off, but wouldn't a united south with say a total of 22 senators been able to filibuster any bill they wanted to death?
But looking back on the events and writings of the day, the tariff did not seem to get any special notice. All the commotion through the 1860 political season, both North and South, was over the expansion of slavery. I have never come across any speeches or newspaper editorials either advocating or lamenting the tariff act. It seemed to be very much a side issue. The south did not secede over tariffs.