Complex sentence: Tyler was a former Democrat and broke bitterly with the Whigs, and named Calhoun Secretary of State on April 10,1844, following the death of previous Secretary of State Abel P. Upshur in the USS "Princeton" disaster.
Split into simpler sentences: Tyler was a former Democrat and broke bitterly with the Whigs. He named Calhoun Secretary of State on April 10,1844, following the death of previous Secretary of State Abel P. Upshur in the USS "Princeton" disaster.