News broke Monday that Republican National Committee Chairman Reince Priebus is calling on NBC and CNN to scrap plans to film documentaries about Hillary Clinton.

If they don't, Priebus said, he will seek a binding resolution at the RNC's meeting next week preventing the party from participating in any debates sponsored by the two networks -- a pretty significant threat.

So where is this coming from? And why is Priebus picking this fight?

First of all, there is undoubtedly concern among Republicans that the documentaries will paint Clinton in a positive light. Clinton is coming off a high point in her career (her term as secretary of state) and is broadly popular among the American people.

Second, when it comes to the GOP base, few things play as well as ragging on the mainstream media, which conservatives have long accused of favoring Democrats/liberals. While MSNBC is the right's biggest target these days, conservatives have long complained about CNN's coverage too.

And third, there may be a little revenge at work here.

Numbers on the eve of the 2012 election from the Pew Research Center showed CNN and NBC's cable network, MSNBC, spent more time on stories that painted GOP nominee Mitt Romney in a negative light than any other network.

While 36 percent of CNN's stories about Romney were negative, by Pew's count, just 11 percent were positive.

And while 71 percent of MSNBC's coverage of Romney was negative, just 3 percent was positive.

Pew shows CNN was much more evenly split when it came to President Obama, while MSNBC's coverage of Obama tilted very favorably in the president's direction.

(On the flip side, Fox's coverage tilted heavily in Romney's favor and was very critical of Obama.)

MSNBC, of course, has much more of a viewpoint than NBC does. When it comes to the broadcast network, Pew numbers show NBC was on-par with other broadcast networks' coverage of Romney and that it was actually about as hard on Obama as it was on the GOP nominee.