President buchanan was denounced by republicans as a a prosouthern democrat

doughface

Explanation:

Term doughface implies a person, most usually a politician, who is impressionable and easy to sway in his ideas. More concretely, this term was used to describe the Northener democratic politician who is allied with the Southerner democrats more than Northen ones.

President Buchanan became known by this name because of his politics that preferred the South. For his cabinet, he chose the majority of the people who were southerners, and even those three from the north were considered also to be doughface. He held very pro-southern principles. These ideas were seen unfavorably by the North and his Democratic party and therefore divided it.