Democrats are pulling away in the generic ballot. What does that mean?

Despite all the unusual political events of the last few years, one thing in electoral politics is proceeding by the book: the growing Democratic advantage on the generic congressional ballot.

The generic ballot is a poll question that asks voters whether they’ll vote for Democrats or Republicans for Congress, and historically it’s been a decent predictor of the House popular vote. Democrats now lead by over 13 points, according to the FiveThirtyEight generic ballot tracker, after a CNN/SSRS poll on Wednesday gave Democrats a staggering 18-point edge, 56 percent to 38 percent.

A 13-point edge would be similar to or larger than their advantage in 2006, when Democrats won control of both the House and the Senate.