And as Alexander Stephens pointed out so clearly in his December 1860 speech to the Georgia Secession Convention, Lincoln did not have to power to pass any legislation or even name his cabinet without southern support. The Republicans were a minority in congress. The Morrill Act only passed congress because 11 southern states had withdrawn their deligations.
You are spreading half truths. The Morrill Act passed the House well before even one single southerner had left congress. The vote fell precisely on sectional lines, perhaps more than any other vote before the war. Only 1 southerner favored the thing, with otherwise unanimous southern opposition. The situation was opposite with near unanimous northern support, be they democrat or republican.
By 1861 the situation was clear. The incoming president wanted the tariff and had indicated he was going to push for it heavily. The senate was sectionally split almost down the line, but with the North lining up behind the thing practically unanimously a vote to pass it was definately in reach no matter what southern states had left or not.