The use of "retractar" is quite formal and doesn't quite work as well in Spanish as in English, as it is often used as a reflexive verb ("retractarse") with the meaning "to take back one's word". The verb "retirar" (to take back) is often used for this context (even in formal speech) and sounds more natural. The option "rectificar" (rectify, correct) is also very commonly used for voting, but I feel it can be understood as "retract AND vote again".