Complex sentence: From December 1873 until the expiration of his term in 1877, Stevenson was generally recognized as the chairman (later known as the floor leader) of the minority Democratic caucus in the Senate; he was the first person to have acted in the capacity.
Split into simpler sentences: From December 1873 until the expiration of his term in 1877, Stevenson was generally recognized as the chairman (later known as the floor leader) of the minority Democratic caucus in the Senate. He was the first person to have acted in the capacity.