On the Democratic side, Bernie Sanders spent the first part of 2015 categorized as a likely loser who received very little media attention (indeed, the whole Democratic contest received relatively little attention until it became competitive). But once he gained traction, Bernie got some media buzz, and it wound up giving him the most positive media coverage of any candidate in either party, at least through 2015:
As his poll numbers ticked upward, [Sanders] was portrayed as a “gaining ground” candidate, a favorable storyline buttressed by reports of increasingly large crowds and enthusiastic followers. “The overflow crowds Sanders has been drawing in Iowa and New Hampshire,” said USA Today, “are signs that there is ‘a real hunger’ for a substantive discussion about Americans’ economic anxieties … .” The “real hunger” extended also to journalists, who are drawn to a candidate who begins to make headway against an odds-on favorite.
Sanders’ coverage in 2015 was the most favorable of any of the top candidates, Republican or Democratic. For her part, Hillary Clinton had by far the most negative coverage of any candidate.
https://nymag.com/intelligencer/2016/06/positive-2015-media-coverage-for-sanders-trump.html
https://shorensteincenter.org/pre-primary-news-coverage-2016-trump-clinton-sanders/