Suikoguy
I whinny my fervor lowly, for his length is not as great as those of the Hylian war stallions
There is no source. It's mostly speculation as to why only 6 primary debates are scheduled and why the debates are scheduled on weekends. A general analysis can conclude that it's a high possibility that the debate schedule is poor because of favoritism, but of course nobody is going to come out and say that.
However, the desire for less debates is actually cross-partisan. Both the Republicans and the Democrats scheduled less primary debates for this round compared to previous elections.
I think 6 debates is pretty solid in the information age we are in now. I do have some criticism on the 'timing' of the debates.