You are more likely to vote for a candidate that looks like you – or rather you are more likely to vote for a candidate that you think looks like you no matter what they really look like. In this experiment researchers morphed voters faces into one of the two candidates. When shown the morphed picture, voters were much more likely to vote for that candidate a week later.
For an example of morphing, check out the Smart Mobs blog post. They posted a couple of examples of faces morphed into the presidential candidates.