Democrats have overperformed by an average of nine points in each of the eight special elections since President Trump took office — giving us a sense of what a blue wave might look like in November. This map shows the scenarios for the House races if the Democratic voter turnout resembles the special elections.
Yes, but: Past performance doesn't guarantee future outcomes. A 9-point swing would put the 2018 House race on par with Republican waves in 1994 and 2010, but the generic ballot isn't as favorable. Real Clear Politics had the Democrats up by 13 in December 2017, but by end of this month, their lead was down to 4 points.