Political predictions rely on polls. Polls are known to have accuracy issues.How they pick random people to poll, one demographic being less inclined to take the poll than another, people who lie, vague or misunderstood questions, questions that require a black or white responses that doesn't account for a more nuanced answer to name a few. Which is what pollsters try to adjust for.
Baseball uses numbers from past performance. Much less ambiguity. All I'm saying is they could add one more cold hard fact. Calculate the variance of past performance against the model used to assess future performance then use it in your next projection.