Complex sentence: Spooner and fellow Wisconsin Senator, Robert M. La Follette, were known to be bitter rivals, Spooner disagreeing with La Follette's progressive policies, which were opposed to his own conservative policies.
Split into simpler sentences: Spooner and fellow Wisconsin Senator, Robert M. La Follette, were known to be bitter rivals. Spooner disagreed with La Follette's progressive policies, which were opposed to his own conservative policies.