Computing party losses

Stanford political scientist Richard Brode's formula for midterm House losses: 6.6 seats plus 0.9 times the Gallup opinion change. Reagan dropped 10 points between January 1981 and mid-August 1982. This works out to a 15.6 seat loss in the House in 1982 - 6.6 + (0.9 x 10). In the Senate, Brode credits a president with a 2.25 seat gain, then subtracts 0.26 times the approval change. This works out to 2.25 - 2.6 = - 0.35, basically no change in the Senate. These estimates are close to those of party officials.