Choose to veto, possibly (4)
I believe the answer is:
vote
I believe this is a double definition.
'choose' is the first definition.
(I know that choose is a is a more specific form of the action of vote)
'veto possibly' is the second definition.
(I know that veto is a type of vote)
'to' acts as a link.
(Other definitions for vote that I've seen before include "Make cross" , ""X" marked on election day" , "Mark on ballot paper" , "Put one's cross" , "Mark choice in election" .)