First, the words predict and forecast are not interchangeable. Polls do not predict outcomes, they merely forecast them. Since predictions are purely subjective, saying they 'failed' is inappropriate. You can disagree with a subjective prediction, but you can't really say they failed. Forecasting relies on historic data to extrapolate. That same data basically said "its a 50/50 coin toss" so the polls did not, in fact, fail. You just thought they failed because the precise poll value was not 50/50, but rather 49.xx/51.xx which does not account for statistical variances.