The correct answer is A) the confirmation bias.
This is an example of confirmation bias.
That is why it is so important the campaign team take into consideration all these factors to create the best messages and campaign ads during the political campaign.
Voters tend to have an image on the preferred candidate and it is difficult to modify that perception although something big happens. They love their candidate and that's it. It could have the same or worts mistakes or attributes than the rival candidate, but they do not recognize them and only see the defects on the opposite candidate, confirming the bias.