Dark blue indicates heavily Democratic votes. In 1976, when the Democrats maintained control of the House, the distribution of winning margins is fairly even, from the Democrats winning by 60 points to Republicans winning by about 40. Republicans won races by closer margins. Overall, Republicans had more unnecessary votes (that is, more votes than needed for a victory) than Democrats did. But even while losing the House by a wide margin, more than 60 Democrats won by more than 50 percentage points.

Source: Washington Post March 27, 2018 19:25 UTC