Entry in progress—B.P.
 
Merriam-Webster Online Dictionary
on the fence: in a position of neutrality or indecision
   
The Free Dictionary
Idiom:
on the fence Informal
Undecided as to which of two sides to support; uncommitted or neutral.
     
Thesaurus.com
Main Entry:  on the fence
Part of Speech:  adjective
Definition:  undecided
Synonyms:  ambivalent, betwixt and between, blowing hot and cold, borderline, debatable, divided, hemming and hawing, hesitant, iffy, impartial, in the middle, indecisive, irresolute, neutral, not definite, not sure, of two minds, open, running hot and cold, tentative, torn, uncertain, unclear, uncommitted, undetermined, unsure, up in the air, waffling, wavering, wishy-washy
 
(Oxford English Dictionary)
fence, n.
chiefly U.S. (to stand or sit) on or upon the fence: (to be) undecided in opinion, or neutral in action
1828 Richmond Whig 13 Aug. 1/5 (Th.), There are certain Administration Editors, Editors for a long time on the fence, who occasionally undertake..to sit as censors upon their fatigued and dusty brethren.
1829 R. C. SANDS Writings (1834) II. 160 Mr. Spratt..was ‘on the fence’; where, like a wise man, he determined to sit, until he had made up his mind on which side to get off.
1830 Annals of Cleveland No. 316, Now all would-but-dare-not-be-politicians who insist in sitting on the fence, will be amerced a penalty for the same.