Trump's behavior at this debate is why the Republican Party is now defined by who else can be added to the list of those to hate, who else can be attracted to the Republican view by supporting their racism, misogyny, or by demonizing a person they disagree with - like Obama or Clinton.  The ugliness of politics today, the shear fact that Trump now represents the Republican Party, is the child of Republican tactics - divide and conquer, trash and demonize the opposition.  

What is most dangerous about Republican tactics is that it is closer to fascism than it is to democracy - Trump made that clear with his remarks about assigning a special prosecutor to jail Hillary Clinton if he is elected.  McConnell made it clear when Obama was elected that he would oppose him on everything.  Trump is a product of, a creation of, those running the Republican Party.

Trump only appears to be an aberration of a Republican politician.  He is the epitome of what the Republicans have created.