I think, as most here probably do, that the MSM is vastly underestimated Bernie's base, especially in a fractured field. In poll after poll, Sanders drastically leads with voters who are sure of their candidate preference. His campaign this time around is much better run than his 2016 campaign, and they have much more popular surrogates this time who will swing votes.
How fractured is the field, really? By mid-February we'll probably be down to half a dozen candidates, by March three or four. Results in the low twenties, or even in the mid twenties, aren't going to win in a four way race, and certainly not in a three way race.
The field is fractured enough that you could win pluralities with 35-40% support, sure. Not with 20-25%.