Complex sentence: Eleanor Roosevelt flew to the convention to try to repair the damage in the Roosevelt-Farley relationship, and although Farley remained close to ER and Jimmy Roosevelt, he felt betrayed by FDR and refused to join FDR's 1940 campaign team.
Split into simpler sentences: Eleanor Roosevelt flew to the convention to try to repair the damage in the Roosevelt-Farley relationship, and although Farley remained close to ER and Jimmy Roosevelt. He felt betrayed by FDR and refused to join FDR's 1940 campaign team.