Complex sentence: He was the "old guard" candidate at the 1938 Conservative leadership convention coming in last place due to a rush by many of his delegates to support Murdoch Alexander Macpherson in an unsuccessful attempt to stop Robert James Manion from becoming leader.
Split into simpler sentences: He was the "old guard" candidate at the 1938 Conservative leadership convention. He placed last after many of his delegates decided to support Murdoch Alexander Macpherson in an unsuccessful attempt to stop Robert James Manion from becoming leader.