I know some people don't like Nate Silver, but here is an excerpt from one of his recent articles about the primary polls:
In a sense, the primaries are a lot like the NCAA basketball tournament: You know there are going to be some surprises. The odds of every favorite winning every game in the NCAA tournament are longer than a billion-to-one against. And yet, in the end, one of the front-runners usually wins. (Since the men’s tournament expanded to 64 teams in 1985, all but three champions have been No. 4 seeds or better.)
So be wary of grand pronouncements about What It All Means based on a handful of “surprising” developments. Is Scott Walker’s campaign off to an “unexpectedly” bad start, for instance? Maybe. (I wouldn’t be thrilled if I were one of Walker’s strategists. I’d also remind myself that we have five months to go before the Iowa caucuses.) Even if you grant that Walker is having some problems, however, it would be stunning if all the Democratic and Republican campaigns were doing exactly as well as pundits anticipated. At any given moment, some campaigns are bound to be struggling to meet expectations, or exceeding them.
Similarly, while one might not have predicted that Bernie Sanders would be the one to do it, it was reasonably likely that some rival would emerge to Hillary Clinton. It’s happened for every non-incumbent front-runner in the past: Buchanan for Dole; Bill Bradley for Al Gore.
The other big difference between the general election and primaries is that polls are not very reliable in the primaries. They improve as you get closer to the election, although only up to a point. But they have little meaning now, five months before the first states vote.
It’s not only that the polls have a poor predictive track record — at this point in the past four competitive races, the leaders in national polls were Joe Lieberman, Rudy Giuliani, Hillary Clinton and Rick Perry, none of whom won the nomination — but also that they don’t have a lot of intrinsic meaning. At this point, the polls you see reported on are surveying broad groups of Republican- or Democratic-leaning adults who are relatively unlikely to actually vote in the primaries and caucuses and who haven’t been paying all that much attention to the campaigns. The ones who eventually do vote will have been subjected to hundreds of millions of dollars’ worth of advertising, had their door knocked on several times, and seen a half-dozen more debates. The ballots they see may not resemble the one the pollsters are testing since it’s likely that (at least on the GOP side) several of the candidates will have dropped out by the time their state votes.
(emphasis mine)
I think that these poll number reflect name recognition more than anything else. You have Trump, who gets breathless coverage in the media leading in the polls, even though he has the highest unfavorables. On the dem side you have Hillary and Biden who get substantial news coverage (although it seems most of Hillary's is negative these days). So yeah, this pretty much explains why these people are leading right now. I'm willing to bet the farm that the polls wont look that way come February 1st.
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