Sentence:  Lady Margaret Beaufort's third husband, Lord Stanley, an accomplished political <WSD>trimmer</WSD>, gave fair words but little commitment: the vast, well-armed Stanley retinues shadowed Henry's route southeast to the battlefield and waited, detached, to see how the chips fell. 
Meaning of the word marked with <WSD> tags:  Someone who fluctuates between opposing factions, political parties etc., according to current interest, a flip-flopper.