But Reagan and Clinton won re-election, unlike two of the nonactivists, George H.W. Bush and Carter. This suggests that there is some sort of balancing mechanism at work, some concern about whether a president has too much power. But the concern doesn't manifest itself strongly if the president isn't a strong force. The more active presidents are the ones most likely to generate a strong backlash in the midterm. Ironically, though, activism also seems to foster re-election of the president.
People see a strong leader, which they want.
The forces at work in a presidential election seem to be different from those in a midterm. It's a theory. It cannot be proven on the basis of the handful of elections noted here. Still, the numbers are suggestive enough to be worth pausing over. Clinton, upon election, proceeded as if he had a mandate for change.