My favorite part (talking about both sides) is how the insult is always followed up with a straw man profile of the other person that is the WWI propaganda-poster-of-the-enemy version of whatever they represent
I disagree that the democrats do this. For all the issues I have regarding the left, the democrats are very good at guarding their own while the republicans tear each other down during their race to the top.
Just look at the difference during the debates. How often do you hear Bernie Sanders rip into Hillary? He even downplayed the email server issues that was plaguing Hillary.
The Republicans can learn a lot by watching how the Democrats treat each other.