Some applicable findings from me.

We have two (free) daily rags here in DC.
From reading both I can honestly say that one is right leaning and one is left leaning.
An observation on the intelligence of the readership of both rags based on doing the crosswords:

The left leaning rag I have to think to finish.

The right leaning rag is far easier to complete and I've yet to learn anything from it.

This would seem to indicate that the right leaning rag thinks it's readers are not as well educated(stupid).