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.