Complex sentence: He was an unsuccessful candidate for election to the Fifteenth Congress to fill the vacancy caused by the death of Peterson Goodwin, but was elected as a Republican to the Sixteenth and Seventeenth Congresses (March 4,1819-March 3,1823).
Split into simpler sentences: He was an unsuccessful candidate for election to the Fifteenth Congress to fill the vacancy caused by the death of Peterson Goodwin. Jones was elected as a Republican to the Sixteenth and Seventeenth Congresses (March 4,1819-March 3,1823).