A shorthand explanation for midterm elections has long been that they are “referenda on the incumbent president.”
The theory postulates that the party of the White House has lost House seats in 36 out of 39 midterms since the Civil War and Senate seats in 19 out of 26 midterms since the direct election of senators began in 1914 because voters are typically unhappy halfway through a presidential term.
The reality, however, is that this oft-used phrase may better describe the effect than the cause. CONTINUED
Charlie Cook