Why would Henry Clay, John C. Calhoun, and Daniel Webster have been effective at keeping the Union together?

Around 1832 and 1833 The United States was involved in a Nullification Crisis - confrontation between South Carolina and the federal government. In this crisis, something bigger was at stake, the Union. It was a clear crisis between the North of America - that abolished slavery - and the South - that didn't and didn't plan to do so. The crisis got worse when South Carolina threatened a secession from the Union if the federal government attempted to enforce tariffs.

This is when Henry Clay, Daniel Webster, and John C. Calhoun show their importance. Henry Clay viewed that the disunion and an eminent civil war were a great danger for the Nation. He negotiated with northern protectionists - Daniel Webster - and with Southern nullifiers - John C. Calhoun and reached an agreement with a new tariff. This delayed the civil war and made possible for the North expand and strengthen its industries.