Who is Augustus McCrae from Lonesome Dove and what is their importance?

Married twice, Augustus McCrae is not as a young man anymore to look at, but his spirit stays young and fanciful. His hair is gray and he's seen more time go by than he cares to think about. He doesn't believe in hard work, and would rather spend his time on the porch with a good jug of mash, exercising his mind. He would have married a third time, Clara having turned him down when he asked her, and he still tells people that she made a mistake saying no. Jake and he both vied for Clara's affections and neither won.