U.S. Election forecasting guru Nate Silver's forecasting firm http://fivethirtyeight.com, that got the 2015 UK general election just as badly wrong as he the previous 2010, have been busy putting up a smoke screen of excuses as to why they got it wrong once more
And just in case we are inclined to say, "Oh, that was just push-polling stuff; the Independents and disenchanted Dems will break for Trump against Hillary," I would offer another very important data set that is NOT corrupt.
I am referring to the fact that Trump has never broken the 50% level with the Republican base--and this despite his vaunted momentum from a string of victories (which would ordinarily put him over 50% well before now). My point here is that Trump has an oddly low ceiling of popularity even with Republicans.
This distinct and stubborn dislike of Trump by the majority of Republican voters would tend to give credence the claims made in other polls that Trump's overall national popularity is terrible, even lower than Hillary's, perhaps.
I can personally assure you that Trump's unpopularity with Republicans is not just a matter of Trump's unpopularity with GOPe guys. In the conservative circles I live and work in, we don't like the GOPe--but we don't like Trump, either.
We regard Trump as another weird sort of RINO, this time a RINO who could finally seal our national doom by his ego--i.e., daring to take on Hillary when he has burned too many bridges with Constitutional conservatives.