CNN had highest score during convention. Stands to reason.
Even the mainstream media acknowledges CNN attracts more Dems. THus, it is no surprise they beat Fox, though Fox did better for all-day ratings still.
I was more curious over the three networks as a whole. Like I said, Limbaugh has been making a big joke over the ratings for the networks coverage of the convention. Well, they are just covering one hour a night. I assume that anyone who is really interested - Democrat, Republican or whatever - is going to start watching the coverage on one of the three news networks and isn't going to bother switching to ABC, CBS or NBC. Anyone not intersted in not going to bother with the abbreviated coverage and will tune out at 10 PM. An increase in CNN, FOX or MSNBC ratings would seem to confirm that.