As the Virginia House of Delegates Goes, So Goes the Nation?

As presumably everybody knows at this point, the Republicans got crushed in races for the Virginia House of Delegates on November 7, losing at least 15 seats (in a 100 seat body). But that's just Virginia right? It can't possibly mean much for the nationwide elections in 2018.

Or can it? Political scientist Steven Rogers asserts that, in fact, outcomes in Virginia House of Delegates election are actually quite predictive of results in the next midterm elections. Here's the bottom line:

[T]he fortunes of the president’s party in Virginia House elections are related to how the president’s party fared in midterm elections the next year….a clear correlation emerges in U.S. House and state House elections.

A 10-point change in seats in the House of Delegates is associated with a 4-5% seat change in midterm state House and U.S. House elections…. the predicted loss in Republican seats [in 2018]….would be almost as large as Democratic losses in 2010 and exceed Republicans losses after Watergate in 1974.

 Thank you, Virginia.