Who is Senator Lister Ames Rosewater from God Bless You, Mr. Rosewater, or, Pearls Before Swine and what is their importance?

Senator Lister Ames Rosewater is the creator of the Rosewater Foundation and the one who determined the rules in its charter. He is a senator from Indiana. As the story unfolds, the Senator comes to question his son and why he hates him. He tries to help him at the end before the sanity hearing.