while remaining true to his principles 
(ROOT (SBAR (IN while) (S (VP (VBG remaining) (ADJP (JJ true) (PP (IN to) (NP (PRP$ his) (NNS principles))))))))
(ROOT (SBAR (IN ) (S (VP (VBG ) (ADJP (JJ ) (PP (IN ) (NP (PRP$ ) (NNS ))))))))