Complex sentence: Caldwell was elected as a Democrat to the Sixty-fourth, Sixty-fifth, and Sixty-sixth Congresses (March 4,1915-March 3,1921): declined to be a candidate for renomination in 1920.
Split into simpler sentences: Caldwell was elected as a Democrat to the Sixty-fourth, Sixty-fifth, and Sixty-sixth Congresses (March 4,1915-March 3,1921). He declined to be a candidate for renomination in 1920.