The media? Nothing. The free press? Journalistic ethics and tradition.
Keep in mind that the media in America are corporate owned and that corporations are government contrivances. They have nothing whatsoever to do with journalism or with a free press.
There is no obligation to "equally cover" misdeeds. I'm not sure what you mean by that. If a candidate shoots somebody and the shooting is covered by ABC, is CBS obligated to cover that misdeed? No obligation entails, but of course the coverage will occur anyway.
You may be referring to the right-wing claim that Hillary is not as covered re her emails, Benghazi, Syria, etc., as much as Trump is covered for his various outspoken remarks and claimed sexual assaults. That's probably true but no obligation exists to provide equal coverage in such a case.
The media is driven by profits (ratings) and Trump has been an enormous draw for media ratings - much greater than Hillary so he gets the lion's share of coverage - negative tho it often is.
(I use "Hillary" instead of "Clinton" to avoid confusion with her husband).
Nothing. There are no longer standards. Those days are over it seems. Glad I didn't use my college years for a profession that has disappeared. The media now is just employees furthering someone's agendy.
Randy D 