The Morrill tariff was signed into law before Lincoln took office by a Democratic president. It was passed AFTER the slaveholding South seceded, therefore was not a cause of the war. The Morrill tariff was bottled up in committee by the South before it's passage and more than likely would not have been passed by the Senate had the Southern representatives had stayed and done their job. The issue contains none of the fervor and depth in ANY secession document that slavery does and it is slavery that dominates in those documents.
Not only is the tariff not as important as slavery as an issue for secession, it is feeble and almost non existent.
Type the word "tariff" in this forum's search feature and see how many times this theory has been debated, discussed, and disposed off in they many threads it is brought forth.
The Morrill tariff should not be used as some form of excuse as a political flavoring of the main dish of slavery which was the issue that brought on the war.
So was it secession that caused the war?