http://www.slate.com/articles/news_and_politics/politics/2015/10/martin_o_malley_jim_webb_and_lincoln_chaffee_s_first_democratic_debate_how.html

LAS VEGAS—Donald Trump has changed a great many things about the way presidential primaries are supposed to work. Most obviously, he isn’t supposed to still be around right now. He’s also skewed people’s expectations of what’s supposed to happen in a first presidential debate. Typically we’d get a bit further into the season before candidates start directly insulting each other about their looks. If we recall any election before this one, we would remember that the first debates are supposed to be the ones in which candidates “introduce themselves to the country.”