The media are pumping Trump because (a) he's very good at coopting them to do his bidding - see The Apprentice (i.e., he's "us" as far as the media is concerned), and (b) it makes for really good trash-talk theatre - think National Inquirer level discussions - and it makes the GOP look like a bunch of blithering idiots, all of which does play into the hands of the DNC. In other words, the media are using Trump as a foil to set the tone - the narrative - for the 2016 elections, in which the GOP will, once again, be portrayed as a bunch of angry, bitter, out-of-touch, racist, antediluvian crackpots. And Trump is certainly helping to construct that narrative.