I'm asking what you mean by "probability" and "chance", but it sounds like the answer is that you don't have any idea, because you've never studied statistics even to the point of taking an introductory class. At this point you've explicitly rejected foundational axioms of both frequentist probability and Bayesian probability, with no apparent awareness that this means you have rejected the entire field of statistics.
You’re missing the point. Axiomatic systems aim to be internally consistent. The question is whether they are good model of a real life situation. Your technical knowledge is distracting you from the more fundamental questions.
There is no sense in which Harris had a 50% chance and had an unlucky day. The only “chance” going on is how likely the poll sample represents the population. The math behind that assumes you have a genuine sample and ignores realities like preference falsification.
Please think and read charitably before making personal attacks. I generally take that as a sign you are acting in bad faith and I do not want to interact with you. Goodbye.