It’s more difficult than ever to tell who is going to continue in the runoff after the October 5th. After Marina’s campaign mate’s death, a big chunk of the electorate have been persuaded towards the alternative between PT and PSDB.
The values I used to start the chains, my initial beliefs, were that Dilma would receive somewhat 40%, Aécio ~ 25%, Campos/Marina ~ 20%, Others ~ 6, and Nulls ~ 8%. The MCMC was run for 1000 election, with a learning period of 500.
The following charts were produced using the forecast model I’ve been working on, which includes national as well state polls. Note that the model is naïve as it doesn’t include any other source of information. That is, I’m attempting to forecast the election based only on the mood of the electorate as captured by many pollsters.
The dots crossed by a vertical line on the charts represent my prior expectations for the election outcome. The colored area represents 95% of confidence interval for the day-to-day changes on the vote intentions. The “+” signs show the measurement evidence from the polls. The area between the last poll and the dots (roughly the September month) is the uncertain are I’m trying to foresee.
Note: Although Marina should have be lower according to my expectations, she is actually going up. She can even go further given the bad news regarding the economy performance, which the government doesn’t seem to have a coeherent explanation for the poor growth. Some says the World Cup was the vice, other say the World Cup was a virtue, and still others insist to say that the culprit is the international crisis. That one in 2008.