Actually, when I lived in Tucson during the Mo Udall days, he was known as a liberal who would say one thing at home and vote the other way in congress. The local and national media tried to make him the "oh shucks," type of good ol boy, but anyone who used the term, "progressive" as much as he did made many people wary.
He was almost beaten one year by an ex-POW, but the local Republican party dropped the ball and didn't give Udall's challenger much support.
There was a push from some inside the Democratic party to get Mo to run for President. In spite of his reputation for a quick wit, he was also rumored to be 'difficult', so the party bosses took a pass.