Now it's absolutely true, and I agree with Professor DiLorenzo, that the Republican Party could never have been successful without the support of the tariff interests involved. The Free Soil Party and the Liberty Party were anti-slavery parties, which were, you might say, pure in their principles, but they had no chance of being successful on a national basis. It was the addition of the tariff interests that gave the Republicans the ability to carry their anti-slavery program into action. And it's in that light, I think, that you have to look at the whole question of the tariffs.

The Real Abraham Lincoln: A Debate (2002)