Odds for the Brazilian 2018 president elections: An application of Bayesian statistics in contingency tables

The purpose of these notes is to present an assessment of the probability of a candidate be elected in a two-round presidential election. In the first round, all candidates can be voted on. If one of them has more than 50% of the vote (s)he is elected and there is no second round. If none of the candidates obtain more than 50% of the votes, then the top two candidates will be selected for a second round. In this second round, the most voted candidate is elected. This is the scenario of the Brazilian elections that are taking place at the moment. We are calculating the odds associated with the 2018 presidential elections in Brazil. The first round is on October 7, and the second round is on October 28, 2018.