I doubt it will happen. From what I'm reading and messages from relatives, federal police is blocking access to the voting polls in some poor areas where Lula is popular.
I don't think the PRF has enough people to actually make a difference in that blockade. Having said that, these are truly dark times for our democracy.
Futures markets favor Lula 10:1. Do you have reason to doubt the herd?
Futures markets tend to be quite awful at predicting military dictatorships, and are even quite keen on right wing fascism. Take everything with a grain of sand. Not just tonight, where the results will be announced, and Bolsonaro will protest them if he doesn't win, but even in the upcoming years.