What is the term used for special elections?
By-elections
Why are they special?
do not always occur on Election Day
What sways these elections?
candidate characteristics
What is the main thing?
presidential approval
How do you know?  What was done?
increased in magnitude
When was the study done?
2016
On all elections or specific ones?
specific
On what offices?
United States House of Representatives
Is it having more of an impact over time?
Yes
What year was the turning point?
2002