worst case scenario

Romney v. Clinton: if these are the nominees of the Janus-faced party in November, an interesting question presents itself: will more votes be cast for positive or negative reasons?

To be more specific, suppose we exclude from consideration all though who both endorse one candidate unreservedly and despise the other unreservedly. Of the remaining voters, will those who vote because of their positive feelings toward a particular candidate outweigh those who vote solely out of negative considerations (the lesser of two evils, as it were)? If not, would this reflect poorly on our electoral process and the 2-party system? Or, perhaps, on the increasing role of media coverage in the electoral process?