Political mudslinging has been part and parcel of our electoral process since the beginning. Thomas Jefferson hired a writer to make claims that John Adams was a repulsive pedant and a hideo s hermaphroditical character. Davy Crockett accused Martin Van Buren of wearing women's corsets. For a fun read on these types of things, go here.
Newspapers have a long tradition of supporting one candidate or another but we always expected them to tell the whole truth when reporting the news. In reality people like William Randolph Hearst have always slanted their media empires. These days the right wing considers the NY Times and the Washington Post to be standard bearers for the left. An interesting factoid - the Washington Post is owned by Jeff Bezos - the uber wealthy scion of Amazon.
Media bias seems much worse in the current climate because of the prevailing 24 hour news cycle. That is a byproduct of the news for profit competition that is so prevalent these days. Every media provider is on the hunt for the next new story and cable news is the engine that drives the cycle, along with Internet media companies like Breitbart News, Huffington Post, Politico and others.
Talk radio is, for the most part, the bastion of the right wing in this country. The left has tried but not been successful at establishing a foothold in radio. The airwaves are ruled by Ruch Limbaugh, Laura Ingraham, Sean Hannity, Mark Davis and others.
Cable news' distribution is more balanced with Fox on the right and MSNBC and CNN on the left. Of course the right claims CBS, ABC and NBC are all biased against the right. I find the news operations of most of the networks report the news fairly but when it comes to their personalities - the Tucker Carlsons, Sean Hannitys, Chris Mathews, Rachel Maddows and Keith Olbermans, etc. are proud flag wavers for the right or left. Do not expect anything truly fair or balanced from them.
Long story short, pretty much all media is biased. Anyone who single sources their information is quite frankly a fool IMHO. Even for political junkies like me, it's a jungle out there.
I do not think this situation will change anytime soon, so it behooves us as consumers to be smart about our news intake. Fact check regularly.