It's not just about the polls - it's about the media trying to minimize the impact Trump is having on this race.
I don't think Trump will win the nomination, though I'm not ruling it out. However, I think his presence is making it much more likely that someone like Ted Cruz gets the nomination over more establishment-friendly choices.
Has the anti-establishment sentiment spread to purple and blue state Republicans to allow Cruz to win post March 15th?
The week ending Tuesday, March 15 is where Florida looms, and its status as a later state this year is good news for Rubio and Jeb, or rather for Rubio or Jeb (assuming only one of them’s still in the race), because it’s relatively delegate-rich (though far less so than Texas or California) and winner-take-all, and an earlier date would force them to fight each other more directly, earlier on, than they’d like (although the past week suggests that Jeb is already feeling the need to do that). And it comes the same day as Ohio and Illinois, meaning that three of the nine states that have picked a winner in every GOP primary since 1976 – two of them crucial general-election swing states – all vote at once (Ohio is also winner-take-all).
If in fact, as many of us now expect, the race comes down to a Cruz-Rubio showdown (in which case Rubio, despite his solid conservative record, will be the candidate preferred by moderate and establishment voters), this is the start of his firewall against Cruz, which in that scenario depends on Florida, the Midwest and the blue states, many of which have late, winner-take-all primaries. A similar dynamic, but possibly with a different map, should play out of the final 2 candidates standing are one more insurgent-leaning and one more establishment-palatable.
After that, the primaries start to space out a bit – Colorado, Indiana, Oregon and Washington each have a week to themselves on the current schedule, and New York has two. Tuesday, April 26 is the big Northeastern/Atlantic prize, dominated by Pennsylvania in the week after New York. If the race drags all the way to the end, like Ford-Reagan in 1976 and Obama-Clinton in 2008, the California-and-New Jersey dominated June 7 primary day should provide someone with a coup de grace.
http://www.redstate.com/2015/10/31/previewing-gop-presidential-primary-calendar/