The difference being Sanders is already running, getting hit pieces from corporate-leaning papers, attacks from Clinton´s campaigners and being under scrutiny by the right. And yet he polls a little worse, equally or better than Clinton in some match ups. Of course that could change after Sanders reach Clinton´s level of awareness, but I am not convinced we will see such a drastic change.
His coverage has been mostly positive or neutral. He is also not the frontrunner. Should he miraculously become the frontrunner that would change.