In before the phony poll group.
The truth is that few of these big-media polls are phony, whether they give Trump a huge lead or Cruz a huge lead. Pollsters simply don’t know how to predict who will come out to the polls and how to proportionately measure them. Worse yet, their attempts to be subjective make them prone to learning the wrong lesson. For instance, in 2012, Romney’s GOTV program was an utter, horrifying technical failure that cost him millions of votes, but most pollsters simply skewed their turnout projections leftward for 2014.
That said, there are some weird shenanigans among some of the smaller polls:
Some pollsters want to make a name for themselves by predicting outcomes rather than measuring poll questions Zogby rose to prominence in the 1990s doing this.
Some campaigns take numerous polls, and only release the ones most favorable to them; given natural margins of error, they can often find an outlier poll that makes them look great.
The final trick is “push-polling.” Pollsters ask a few questions designed to get people feeling one way or another towards a candidate before asking them if they’d vote for that candidate. Normally, in a late-season general election, push-polling doesn’t work so well: people know who they like, and pollsters can only push a couple of percent. ( It’s VERY effective on issues polling because most people can see two sides of any issue.) But I’ve seen some surprisingly mainstream pollsters (NBC, CNN) use push polls in the primary, and when there were so many candidates so marginally known, it’s probably much more effective.
One example of a push poll. (This is only one poll, and I don’t mean at all to suggest that push-polling is behind Trump’s high numbers; it plainly is not.) NBC (IIRC) asked people if they thought keeping Americans safe from terrorists was very important to them, asked them who has taken the boldest stance against terrorism, and then asked them who they wanted to vote for.
Apparently Real Clear Politics has never heard of this poll. Here’s a brand new poll from American Research Group, which RCP recognizes. Trump up by 7.
http://americanresearchgroup.com/pres2016/primary/rep/iarep.html