You know they're going to steal it regardless right? I'm not saying don't vote obviously, but as you said, Fascists will cheat, they may not know the margin, but they'll have a pretty good idea by now.
I'll be very surprised if they even allow you to vote at all, there's very little chance they don't go for martial law, or a declaration of war, whatever it takes to not let you take their power away again. You cannot count on the rule of law to get your country out of this, they've already done away with that.