I think there is some portion of the electorate that does just form some general impression of the candidates, and then casts their votes based on how they feel about them. One of the first televised pieces of evidence for this is some old b&w footage with several women saying: "Kennedy is so good looking," and they planned to vote for him.
Obama got a big white guilt vote this year, people who just felt good voting for a black guy.
Alan Keyes (black vote) swung the election to Obama.