9 districts shift toward Democrats after Pennsylvania election

Conor Lamb at a rally in PA. Photo: Drew Angerer/Getty Images

The Cook Political Report shifted nine Republican House seats across the nation toward Democrats after Conor Lamb's victory in Pennsylvania's 18th district, which Trump won by 20 points in 2016.

Why it matters: There are 114 GOP-held districts less competitive than PA-18, so this shift should put Republicans on "heightened alert," writes Cook Political Report's Dave Wasserman.