Why it matters: President Trump’s low approval numbers and heightened enthusiasm among Democratic voters both point to Democratic success in November. But it probably won’t be a wave of historic proportions, based on Cook Political Report’s latest predictions. At best, it could allow them to win the House while barely shifting the Senate at all.
The back story: As the chart shows, both the House and Senate have nearly always moved against incumbent presidents in mid-term elections. See the big Republican swings against Barack Obama in 2010 and 2014 towards the top right, and, in the lower left quadrant, the Democratic swings against Dwight Eisenhower in 1958 and Gerald Ford in the post-Watergate midterm of 1974.