Nate Silver:

myth is that Trump's victory represented some sort of catastrophic failure for the polls. Trump outperformed his national polls by only 1 to 2 percentage points. He beat his polls by only 2 to 3 percentage points in the average swing state.

there were individual pollsters that had some explaining to do, especially in Michigan, Wisconsin and Pennsylvania, where Trump beat his polls by a larger amount.

But the result was not some sort of massive outlier; on the contrary, the polls were pretty much as accurate as they'd been, on average, since 1968.

FiveThirtyEight's final forecast gave Trump a 3 in 10 chance of winning the Electoral College. Others had 1 in 100 shot.