According to
Wikipedia, Zulia has a weird political system where if the governor is from one party, the other party controls municipal government, which leads to competition to do things better (or sometimes spend more on pork barrel projects). People are moving to its largest city, Maracaibo, even from Caracas.
I'd expect a fairly large turnout in Caracas for Rosales - he claims to be leading in some outlying areas of Greater Caracas.