The key question may be not what Hillary knew but when she knew it.
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(ROOT (S (NP (DT The) (JJ key) (NN question)) (VP (MD may) (VP (VB be) (ADVP (RB not)) (SBAR (SBAR (WHNP (WP what)) (S (NP (NNP Hillary)) (VP (VBD knew)))) (CC but) (SBAR (WHADVP (WRB when)) (S (NP (PRP she)) (VP (VBD knew) (NP (PRP it)))))))) (. .)))
According to current reports, the question is not if, but when did Hillary know about it.
( ( According ( to ( current reports ) ) ) ( , ( ( the question ) ( ( is ( not ( if ( , ( but ( when ( did ( Hillary ( know ( about it ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (VBG According) (PP (TO to) (NP (JJ current) (NNS reports)))) (, ,) (NP (DT the) (NN question)) (VP (VBZ is) (UCP (RB not) (PP (IN if)) (, ,) (CC but) (SBAR (WHADVP (WRB when)) (S (VP (VBD did) (SBAR (S (NP (NNP Hillary)) (VP (VBP know) (PP (IN about) (NP (PRP it))))))))))) (. .)))