I think that a major reason for media screwing with the polls is to create a “horserace” between the two sides by picking up the underdog for a while before returning to reality.
This year, Romney has been impervious to Obama’s assaults but he got a phantom bounce from the DNC Convention. It seems to have quickly evaporated because of the Libya fiasco, so suddenly the media is pumping it up insanely with very skewed ratios of D/R/I.
Now, if Obama does very well in the debates, then he can be carried along a lot longer by the media. If Romney shows up well in the debates—if he just ties Obama by showing himself to be intelligent and able to hold his ground against the POTUS—then there will be the “comeback kid” effect and the polls will evaporate for Obama.
To a great extent the current inflated polls are wishful thinking by the media, because the Debates will seal the deal one way or the other. I am a bit nervous about these debates, since it’s the one thing that might save Obama, especially since the debate format and the questions will try to favor him. Certainly the media will proclaim an Obama victory either way, but unless BHO knocks Mitt out conclusively, I think that this race goes back to being a referendum on Obama’s dreadful record and that the American people will judge him and vote him a LOSER.
I think their goal all along has been to discredit a Romney win and challenge its legitimacy as they did with the Bush "selected not elected" crap. They are trying to undermine his presidency five months out.