The site FiveThirtyEight has an "updating estimate of the generic ballot, based on polls that ask people which party they would support in a congressional election". My question is predictive of the House Popular Vote is the Generic Ballot?

I'd imagine that even at the level of a single individual, the response of an individual to a generic ballot poll may not be predictive of how they'll vote in the actual election, because they may vote based on other characteristics of a congressional candidate other than party affiliation. But does these differences tend to cancel out at the level of the entire national electorate, so that Generic Ballot predicts the House Popular Vote really well? Or is it not very predictive? Have there been any studies on this?